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Bắt đầu vào lúcSunday, 3 April 2011, 09:55 PM
Kết thúc lúcSunday, 3 April 2011, 10:02 PM
Thời gian thực hiện 7 mins 55 giây
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Grade0 out of a maximum of 10 (0%)
Question 1 Chỉnh sửa
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  The time for a worker to assemble a component is normally distributed with mean 15 minutes and variance 4. Denote the mean assembly times of 16 day-shift workers and 9 night-shift workers by $$\overline{X}$$ and $$\overline{Y}$$, respectively. Assume that the assembly times of the workers are mutually independent. The distribution of  $$\overline{X} $$- $$\overline{Y}$$ is

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Question 2 Chỉnh sửa
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Find the standard deviation for the given sample data:
2  6  2  2  1  4  4  2  4  2  3  8  4  2  2  7  7  2  3  11
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Question 3 Chỉnh sửa
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Survey responses of “ good, better, best”.  which type of data is?

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Question 4 Chỉnh sửa
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Find the mean for the binomial distribution which has the stated values of n and p. Round answer to the nearest tenth.

n = 20; p = 3/5
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Question 5 Chỉnh sửa
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Assume that X has a normal distribution with the mean is μ = 15.2 and the standard deviation is σ = 0.9. Find the probability that X is greater than 16.1.
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Question 6 Chỉnh sửa
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The manufacturer of a refrigerator system for beer kegs produces refrigerators that are supposed to maintain a true mean temperature, μ, of 45°F, ideal for a certain type of German pilsner. The owner of the brewery does not agree with the refrigerator manufacturer, and claims he can prove that the true mean temperature is incorrect. Assuming that a hypothesis test of the claim has been conducted and that the conclusion is to reject the null hypothesis, state the conclusion in nontechnical terms.

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Question 7 Chỉnh sửa
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It is desired to estimate the average total compensation of CEOs in the Service industry. Data were randomly collected from 18 CEOs and the 97% confidence interval was calculated to be ($2181260, $5836180). Which of the following interpretations is correct?

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Question 8 Chỉnh sửa
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A bag of colored candies contains 20 red, 25 yellow, and 35 orange candies. An experiment consists of randomly choosing one candy from the bag and recording its color. What is the sample space for this experiment?

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Question 9 Chỉnh sửa
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The probability is 2% that an electrical connector that is kept dry fails during the warranty period of a portable computer. If the connector is ever wet, the probability of a failure during the warranty period is 10%. If 80% of the connectors are kept dry and 20% are wet, what proportion of connectors fail during the warranty period?

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Question 10 Chỉnh sửa
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The amount of pyridoxine (in grams) per multiple vitamin is normally distributed with $$\mu= 110$$ grams and $$\sigma = 25$$ grams. A sample of vitamins is to be selected. What is the probability that the sample mean will be less than 100 grams? Let $$P(Z<-2)=0.023;P(Z<-0.4)=0.421;P(Z<0.07)=0.529;P(Z<0.75)=0.673$$.
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Question 11 Chỉnh sửa
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A card game is played in which the player wins if a face card is drawn (king, queen, jack) from a deck of 52 cards. If the player plays 10 times, what is the expected number of wins for the player?
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Question 12 Chỉnh sửa
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Researchers are concerned that the weight of the average American school child is increasing implying, among other things, that children’s clothing should be manufactured and marketed in larger sizes. If $$X$$ is the weight of school children sampled in a nationwide study, then $$X$$ is an example of
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Question 13 Chỉnh sửa
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In a recent survey, 80% of the community favored building a police substation in their neighborhood. If 15 citizens are chosen, what is the standard deviation of the number favoring the substation?
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Question 14 Chỉnh sửa
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Find the critical value or values of x2 based on the given information.


H1: σ < 0.629

n = 19

α = 0.025

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Question 15 Chỉnh sửa
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A company has 2 machines that produce widgets. An older machine produces 23% defective widgets, while the new machine produces only 8% defective widgets. In addition, the new machine produces 3 times as many widgets as the older machine does. What is the probability that a randomly chosen widget produced by the company is defective?
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Question 16 Chỉnh sửa
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Find the origin data from the sterm-and-leaf  plot

mc003-1.jpg
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Question 17 Chỉnh sửa
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The grade point averages for 10 randomly selected students are listed below. Construct a 90% confidence interval for the population standard deviation, $$\sigma.$$ Assume the data are normally distributed.


2.0 3.2 1.8 2.9 0.9 4.0 3.3 2.9 3.6 0.8

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Question 18 Chỉnh sửa
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For large numbers of degrees of freedom, the critical χ2 values can be approximated as follows:


χ2 = (z + )2,


where k is the number of degrees of freedom and z is the critical value. To find the lower critical value, the negative z-value is used, to find the upper critical value, the positive z-value is used. Use this approximation to estimate the critical value of χ2 in a right-tailed hypothesis test with n =125 and α = 0.01.

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Question 19 Chỉnh sửa
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Which statement is true for the scores of 1, 2, 3, 4, 5, 5, 7, 8, 9, and 10?
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Question 20 Chỉnh sửa
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Parking at a large university has become a very big problem. University administrators are interested in determining the average parking time (e.g. the time it takes a student to find a parking spot) of its students. An administrator inconspicuously followed 130 students and carefully recorded their parking times. Identify the sample of interest to the university administration.
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Question 21 Chỉnh sửa
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The probability that a radish seed will germinate is 0.7. A gardener plants seeds in batches of 11. Find the standard deviation for the random variable X, the number of seeds germinating in each batch.
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Question 22 Chỉnh sửa
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The standard IQ test has a mean of 96 and a standard deviation of 14. We want to be 90% certain that we are within 4 IQ points of the true mean. Determine the required sample size.
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Question 23 Chỉnh sửa
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An archer is able to hit the bull's-eye 55% of the time. If she shoots 8 arrows, what is the probability that she gets exactly 4 bull's-eyes? Assume each shot is independent of the others.
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Question 24 Chỉnh sửa
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Let Z is a standard normal variable, find P(-0.73 < Z < 2.27).
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Question 25 Chỉnh sửa
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The following table shows the political affiliation of voters in one city and their positions on stronger gun control laws.


Favor
Oppose
Republican
0.09
0.26
Democrat
0.22
0.2
Other
0.11
0.12

What is the probability that a voter who favors stronger gun control laws is a Republican?
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Question 26 Chỉnh sửa
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Determine whether the hypothesis test involves a sampling distribution of means that is a normal distribution, Student t distribution, or neither.


Claim: μ = 959. Sample data: n = 25,$$\overline{x} = 951,$$ s = 25. The sample data appear to come from a normally distributed population with σ = 28.

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Question 27 Chỉnh sửa
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Suppose X is a uniform random variable over the interval [20, 90]. Find the probability that a randomly selected observation is between 23 and 85.

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Question 28 Chỉnh sửa
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Find the variance for the given probability distribution.

x

0

1

2

3

4

P(x)

0.17

0.28

0.05

0.15

0.35



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Question 29 Chỉnh sửa
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A machine is set to pump cleanser into a process at the rate of 5 gallons per minute. Upon inspection, it is learned that the machine actually pumps cleanser at a rate described by the uniform distribution over the interval 4.5 to 7.5 gallons per minute. Find the probability that between 5.0 gallons and 6.0 gallons are pumped during a randomly selected minute.

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Question 30 Chỉnh sửa
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Construct the relative frequency distribution that corresponds to given frequency distribution
mc005-1.jpg
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Question 31 Chỉnh sửa
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A new phone system was installed last year to help reduce the expense of personal calls that were being made by employees. Before the new system was installed, the amount being spent on personal calls follows a normal distribution with an average of $700 per month and a standard deviation of $50 per month. Refer to such expenses as PCE's (personal call expenses). Find the probability that a randomly selected month had a PCE that falls below $550.
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Question 32 Chỉnh sửa
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Find the probability that in 200 tosses of a fair six-sided die, a five will be obtained at least 40 times.
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Question 33 Chỉnh sửa
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The probability that a student at a certain college is male is 0.45. The probability that a student at that college has a job off campus is 0.33. The probability that a student at the college is male and has a job off campus is 0.15. If a student is chosen at random from the college, what is the probability that the student is male or has an off campus job?
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Question 34 Chỉnh sửa
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Find the critical value or values of $$\chi^2$$ based on the given information.

H1: σ < 0.14
n = 23
α = 0.10

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Question 35 Chỉnh sửa
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The probabilities that a customer entering a particular bookstore buys 0, 1, 2, 3, 4, or 5 books are 0.30, 0.20, 0.20, 0.15, 0.10, and 0.05 respectively. For the probability distribution above, find the variance.

(Note: please give the answer as a real number accurate to 2 decimal places after the decimal point.)

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#Thực hiệnĐáp ánTimeRaw scoreĐiểm
1Điểm22:02:23 on 3/04/1100
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Question 36 Chỉnh sửa
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The time between customer arrivals at a furniture store has an approximate exponential distribution with mean of 8.5 minutes. If a customer just arrived, find the probability that the next customer will not arrive for at least 20 minutes.

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Question 37 Chỉnh sửa
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A psychologist claims that more than 75 percent of the population suffers from professional problems due to extreme shyness. Assuming that a hypothesis test of the claim has been conducted and that the conclusion is failure to reject the null hypothesis, state the conclusion in nontechnical terms.

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Question 38 Chỉnh sửa
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An experiment consists of randomly choosing a number between 1 and 10. Let E be the event that the number chosen is even. List the sample points in E.

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Question 39 Chỉnh sửa
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When conducting a t test for the correlation coefficient in a study with 16 individuals, the degrees of freedom will be
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Question 40 Chỉnh sửa
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Suppose that $$X$$ is a negative binomial random variable with $$p = 0.2$$ and $$r = 4$$. Determine $$P(X=20)$$.
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Question 41 Chỉnh sửa
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Many people think that a national lobby's successful fight against gun control legislation is reflecting the will of a minority of Americans. A previous random sample of 4000 citizens yielded 2250 who are in favor of gun control legislation. How many citizens would need to be sampled if a 95% confidence interval was desired to estimate the true proportion to within 5%?
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Question 42 Chỉnh sửa
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Let X represent the amount of time it takes a student to park in the library parking lot at the university. If we know that the distribution of parking times can be modeled using an exponential distribution with a mean of 4 minutes, find the probability that it will take a randomly selected student between 2 and 12 minutes to park in the library lot.
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Question 43 Chỉnh sửa
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A local bank needs information concerning the checking account balances of its customers. A random sample of 15 accounts was checked. The mean balance was $686.75 with a standard deviation of $256.20. Find a 98% confidence interval for the true mean. Assume that the account balances are normally distributed.
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Question 44 Chỉnh sửa
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A basketball player has made 70% of his foul shots during the season. If he shoots 3 foul shots in tonight's game, what is the probability that he makes all of the shots?
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Question 45 Chỉnh sửa
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Let X be a uniform random variable over the interval [0.1, 5] . What is the probability that the random variable X has a value less than 2.1?

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Question 46 Chỉnh sửa
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When considering area under the standard normal curve, decide whether the area to the left of z =0.2 is bigger than, smaller than, or equal to the area to the right of  z = -0.2
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Question 47 Chỉnh sửa
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A machine is set to pump cleanser into a process at the rate of 10 gallons per minute. Upon inspection, it is learned that the machine actually pumps cleanser at a rate described by the uniform distribution over the interval 9.5 to 11.5 gallons per minute. What is the probability that at the time the machine is checked it is pumping more than 10.5 gallons per minute?

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Question 48 Chỉnh sửa
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Find the mode(s) for the given dample data
98,  25,  98,  13,  25,  29,  56,  98
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Question 49 Chỉnh sửa
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If you were constructing a 99% confidence interval of the normal population mean based on a sample of $$n = 25$$ where the standard deviation of the sample $$s = 0.05$$. What is the critical value? Let $$t_{0.005,24}=2.7969;t_{0.01,24}=2.4922;z_{0.01}=2.33; z_{0.05}=2.58$$.
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Question 50 Chỉnh sửa
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One year, professional sports players salaries averaged $1.5 million with a standard deviation of $0.7 million. Suppose a sample of 100 major league players was taken. Find the approximate probability that the average salary of the 100 players exceeded $1.1 million.

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Question 51 Chỉnh sửa
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A random number generator is set top generate integer random numbers between 1 and 10 inclusive following a uniform distribution. What is the probability of the random number generator generating a 7?
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Question 52 Chỉnh sửa
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The probability is 0.7 that a person shopping at a certain store will spend less than $20. For random samples of 28 customers, find the mean number of shoppers who spend less than $20.
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Question 53 Chỉnh sửa
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According to a college survey, 22% of all students work full time. Find the standard deviation for the random variable X, the number of students who work full time in samples of size 16.
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Question 54 Chỉnh sửa
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Construct the cumulative frequency distribution that coressponds to the given frequency distribution
mc006-1.jpg
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Question 55 Chỉnh sửa
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A multiple choice test has 10 questions each of which has 4 possible answers, only one of which is correct. If Judy, who forgot to study for the test, guesses on all questions, what is the probability that she will answer exactly 3 questions correctly?
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Question 56 Chỉnh sửa
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A normal distribution has mean μ = 60 and standard deviation = 6, find the area under the curve  to the right of 64.

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Question 57 Chỉnh sửa
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In a sample of 10 randomly selected women, it was found that their mean height was 63.4 inches. From previous studies, it is assumed that the standard deviation, $$\sigma,$$ is 2.4. Construct the 95% confidence interval for the population mean.

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Question 58 Chỉnh sửa
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The collection and summarization of the socioeconomic and physical characteristics of the employees of a particular firm is an example of
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Question 59 Chỉnh sửa
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A nurse at a local hospital is interested in estimating the birth weight of infants. How large a sample must she select if she desires to be 90% confident that the true mean is within 4 ounces of the sample mean? The standard deviation of the birth weights is known to be 6 ounces.
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Question 60 Chỉnh sửa
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Police estimate that 25% of drivers drive without their seat belts. If they stop 6 drivers at random, find the probability that all of them are wearing their seat belts.
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Question 61 Chỉnh sửa
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Let Z is a standard normal variable, find the the probability that Z lies between 0 and 3.01.
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Question 62 Chỉnh sửa
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A cereal company claims that the mean weight of the cereal in its packets is at least 14 oz. Express the null hypothesis H0 and the alternative hypothesis H1 in symbolic form.

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Question 63 Chỉnh sửa
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A business venture can result in the following outcomes (with their corresponding chance of occurring in parentheses) Highly Successful (10%), Successful (25%), Break Even (25%), Disappointing (20%), and Highly Disappointing (?). If these are the only outcomes possible for the business venture, what is the chance that the business venture will be considered Highly Disappointing?
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Question 64 Chỉnh sửa
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A researcher claims that 62% of voters favor gun control. Assume that a hypothesis test of the given claim will be conducted. Identify the type II error for the test.

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Question 65 Chỉnh sửa
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An employee at the local ice cream parlor asks three customers if they like chocolate ice cream. What is the population?

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Question 66 Chỉnh sửa
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A new phone system was installed last year to help reduce the expense of personal calls that were being made by employees. Before the new system was installed, the amount being spent on personal calls followed a normal distribution with an average of $900 per month and a standard deviation of $50 per month. Refer to such expenses as PCE's (personal call expenses). Using the distribution above, what is the probability that a randomly selected month had a PCE of between $775.00 and $990.00?
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Question 67 Chỉnh sửa
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For a standard normal distribution, find the percentage of data that are more than 1 standard deviation away from the mean.
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Question 68 Chỉnh sửa
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In a random sample of 60 computers, the mean repair cost was $150 with a population standard deviation of $36. Construct a 99% confidence interval for the population mean.
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Question 69 Chỉnh sửa
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Let $$\overline{X}$$ denote the sample mean of a random sample of size n1 = 16 taken from a normal distribution $$N(\mu, 36),$$ and let $$\overline{Y}$$ denote the sample mean of a random sample of size n2 = 25 taken from a different normal distribution $$N(\mu, 9).$$ Compute $$P(\overline{X} - \overline{Y}>5).$$

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Question 70 Chỉnh sửa
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Construct a 99% confidence interval for the population mean, μ. Assume the population has a normal distribution. A group of 19 randomly selected students has a mean age of 22.4 years with a standard deviation of 3.8 years.

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Question 71 Chỉnh sửa
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The claim is that the proportion of drowning deaths of children attributable to beaches is more than 0.25, and the sample statistics include n= 647 drowning deaths of children with 30% of them attributable to beaches. Find the value of the test statistic z using $$z=\frac{\overline{p}-p_0}{\sqrt{\frac{p_0(1-p_0)}{n}}}$$.
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Question 72 Chỉnh sửa
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The systolic blood pressure of 18-year-old women is normally distributed with a mean of 120 mmHg and a standard deviation of 12 mmHg. What percentage of 18-year-old women have a systolic blood pressure that lies within 3 standard deviations of the mean?
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Question 73 Chỉnh sửa
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In one region, the September energy consumption levels for single-family homes are normally distributed with a mean of 1050 kWh and a standard deviation of 218 kWh. For a randomly selected home, find the probability that the September energy consumption level is between 1100 kWh and 1225 kWh.
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Question 74 Chỉnh sửa
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A confidence interval was used to estimate the proportion of statistics students that are female. A random sample of 72 statistics students generated the following confidence interval: Using the information above, what size sample would be necessary if we wanted to estimate the true proportion to within 2% using 99% reliability?
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Question 75 Chỉnh sửa
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The principal of a middle school claims that test scores of the seventh-graders at his school vary less than the test scores of the seventh-graders at a neighboring school, which have variation described by σ = 14.7. Assuming that a hypothesis test of the claim has been conducted and that the conclusion is to reject the null hypothesis, state the conclusion in nontechnical terms.

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Question 76 Chỉnh sửa
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Suppose x is a uniform random variable over the interval [40, 50]. Find the probability that a randomly selected observation exceeds 43.

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Question 77 Chỉnh sửa
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The mean replacement time for a random sample of 12 microwave ovens is 8.6 years with a standard deviation of 2.7 years. Construct the 98% confidence interval for the population variance, $$\sigma^2.$$ Assume the data are normally distributed

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Question 78 Chỉnh sửa
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The number of ounces of soda that a vending machine dispenses per cup is normally distributed with a mean of 12 ounces and a standard deviation of 4 ounces. Find the number of ounces above which 80% of the dispensed sodas will fall.

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Question 79 Chỉnh sửa
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Carter Motor Company claims that its new sedan, the Libra, will average better than 30 miles per gallon in the city. Use μ, the true average mileage of the Libra. Express the null hypothesis H0 and the alternative hypothesis H1 in symbolic form.

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Question 80 Chỉnh sửa
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Which of the following is not true about the standard normal distribution?
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Question 81 Chỉnh sửa
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It has been found that 40% of the employees who complete a sequence of executive seminars go on to become vice presidents. Assume that 10 graduates of the program are randomly selected, find the probability that at least two become vice presidents.

(Note: please give the answer as a real number accurate to 4 decimal places after the decimal point.)

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1Điểm22:02:23 on 3/04/1100
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Question 82 Chỉnh sửa
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Suppose that on a particular multiple choice question, 96% of the students answered correctly. What is the probability that a randomly selected student answered the question incorrectly?
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Question 83 Chỉnh sửa
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The volumes of soda in quart soda bottles are normally distributed with a mean of 32.3 oz and a standard deviation of 1.2 oz. What is the probability that the volume of soda in a randomly selected bottle will be less than 32 oz?
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Question 84 Chỉnh sửa
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Both Fred and Ed have a bag of candy containing a lemon drop, a cherry drop, and a lollipop. Each takes out a piece and eats it. What are the possible pairs of candies eaten?

Create the sample space of possible outcomes.

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Question 85 Chỉnh sửa
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Using Excel to find three quartiles for the given data below:
1,  3,  6,  10,  15,  21,  28,  36.
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Question 86 Chỉnh sửa
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If the probability of a newborn child being female is 0.5, find the probability that in 100 births, 55 or more will be female.
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Question 87 Chỉnh sửa
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Assume that a procedure yields a binomial distribution with a trial repeated n times. Use the binomial probability formula to find the probability of x successes given the probability p of success on a single trial.

n =12, x = 5, p = 0.25
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Question 88 Chỉnh sửa
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A random sample of 10 parking meters in a beach community showed the following incomes for a day. Assume the incomes are normally distributed.

$3.60 $4.50 $2.80 $6.30 $2.60 $5.20 $6.75 $4.25 $8.00 $3.00

Find the 95% confidence interval for the true mean.
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Question 89 Chỉnh sửa
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Suppose a 95% confidence interval for μ turns out to be (1000, 2100). Give a definition of what it means to be "95% confident" in an inference.

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Question 90 Chỉnh sửa
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For the sample below, find the number of observations that are within 1.5 standard deviations of the mean.
2,  3,  5,  5,  6,  3,  6,  5,  6,  9,  2,  5,  3,  5,  6,  3,  5,  6,  6,  9.
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Question 91 Chỉnh sửa
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Use the given information to find the P-value.

The test statistic in a right-tailed test is z = 1.43.
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Question 92 Chỉnh sửa
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On a multiple choice test with 16 questions, each question has four possible answers, one of which is correct. For students who guess at all answers, find the standard deviation for the random variable X, the number of correct answers.
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Question 93 Chỉnh sửa
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The grade point averages for 10 randomly selected students in a statistics class with 125 students are listed below.

2.0 3.2 1.8 2.9 0.9 4.0 3.3 2.9 3.6 0.8

What is the effect on the width of the confidence interval if the sample size is increased to 20?
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Question 94 Chỉnh sửa
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A percentage distribution is given below for the size of families in one U.S. city.
Size
Percentage
2
42.8
3
21.1
4
19.2
5
11.6
6
3.3
7+
2.0

A family is selected at random. Find the probability that the size of the family is 4 or more. Round your result to three decimal places.
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Question 95 Chỉnh sửa
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Which of the following is true about the sampling distribution of the sample mean?

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Question 96 Chỉnh sửa
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Construct a 95% confidence interval for the population mean, μ. Assume the population has a normal distribution. A random sample of 16 fluorescent light bulbs has a mean life of 645 hours with a standard deviation of 31 hours.

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Question 97 Chỉnh sửa
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   Survey responses of nationalities of survey respondents. which type of data is?

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Question 98 Chỉnh sửa
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For a standard normal distribution, find the percentage of data that are between 3 standard deviations below the mean and 1 standard deviation above the mean.
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Question 99 Chỉnh sửa
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Assume that a procedure yields a binomial distribution with a trial repeated n times. Use the binomial probability formula to find the probability of x successes given the probability p of success on a single trial.

n = 4, x = 3, p = 1/6
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Question 100 Chỉnh sửa
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Use the given information to find the P-value.

The test statistic in a left-tailed test is z = -1.83.
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Question 101 Chỉnh sửa
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Assume that z scores are normally distributed with a mean of 0 and a standard deviation of 1. If P(Z > c) = 0.1093, find c.
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Question 102 Chỉnh sửa
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The accompanying table shows the probability distribution for x, the number that shows up when a loaded die is rolled. Find the variance for the probability distribution.

x
1
2
3
4
5
6
P(x)
0.16
0.19
0.22
0.21
0.12
0.10

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Question 103 Chỉnh sửa
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The owner of a football team claims that the average attendance at games is over 67,800, and he is therefore justified in moving the team to a city with a larger stadium. Express the null hypothesis H0 and the alternative hypothesis H1 in symbolic form.

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Question 104 Chỉnh sửa
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The manufacturer of a refrigerator system for beer kegs produces refrigerators that are supposed to maintain a true mean temperature, μ, of 50°F, ideal for a certain type of German pilsner. The owner of the brewery does not agree with the refrigerator manufacturer, and claims he can prove that the true mean temperature is incorrect. Assume that a hypothesis test of the given claim will be conducted. Identify the type I error for the test.

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Question 105 Chỉnh sửa
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A campus program evenly enrolls undergraduate and graduate students. If a random sample of 4 students is selected from the program to be interviewed about the introduction of a new fast food outlet on the ground floor of the campus building, what is the probability that all 4 students selected are undergraduate students?
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Question 106 Chỉnh sửa
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Flip a coin twice, create the sample space of possible outcomes.

 

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Question 107 Chỉnh sửa
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The number of power outages at a nuclear power plant has a Poisson distribution with a mean of 6 outages per year. The probability that there will be exactly 3 power outages in a year is
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Question 108 Chỉnh sửa
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If two balanced die are rolled, the possible outcomes can be represented as follows.

(1, 1) (2, 1) (3, 1) (4, 1) (5, 1) (6, 1)
(1, 2) (2, 2) (3, 2) (4, 2) (5, 2) (6, 2)
(1, 3) (2, 3) (3, 3) (4, 3) (5, 3) (6, 3)
(1, 4) (2, 4) (3, 4) (4, 4) (5, 4) (6, 4)
(1, 5) (2, 5) (3, 5) (4, 5) (5, 5) (6, 5)
(1, 6) (2, 6) (3, 6) (4, 6) (5, 6) (6, 6)

Determine the probability that the sum of the dice is 7.
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Question 109 Chỉnh sửa
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A company has 2 machines that produce widgets. An older machine produces 23% defective widgets, while the new machine produces only 8% defective widgets. In addition, the new machine produces 3 times as many widgets as the older machine does. Given that a widget was produced by the new machine, what is the probability it is not defective?
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Question 110 Chỉnh sửa
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At one college, GPAs are normally distributed with a mean of 2.6 and a standard deviation of 0.4. What percentage of students at the college have a GPA between 2.2 and 3?
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Question 111 Chỉnh sửa
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When is the correlation coefficient zero?
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Question 112 Chỉnh sửa
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For sample sizes greater than 40, the sampling distribution of the mean will be approximately normally distributed
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Question 113 Chỉnh sửa
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Find the critical value or values of $$\chi^2$$ based on the given information.

H1: σ > 26.1
n = 9
α = 0.01

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Question 114 Chỉnh sửa
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To determine the difference , if any, between two brands of radial tires, 12 tires of each brand are tested. Assume that the lifetimes of both brands of tires come from the same normal distribution $$N(\mu, 3300^2).$$ Compute $$P(\overline{X}-\overline{Y} <-2500).$$

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Question 115 Chỉnh sửa
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Find the mean of the following probability distribution.

x

0

1

2

3

4

P(x)

0.19

0.37

0.16

0.26

0.02


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Question 116 Chỉnh sửa
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When considering area under the standard normal curve, decide whether the area to the right of z = 2 is bigger than, smaller than, or equal to the area to the right of z = 2.5.
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Question 117 Chỉnh sửa
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Find the percentile for the data point.

data set: 3  11  8  6  3  3  11  6  3  11  2  11  15  4  9  3  12  8  6  11
data point: 6
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Question 118 Chỉnh sửa
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Find the critical value or values of x2 based on the given information.


H0: σ = 8.0

n = 10

α = 0.01

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Question 119 Chỉnh sửa
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Construct a 90% confidence interval for the population mean, μ. Assume the population has a normal distribution. In a recent study of 22 eighth graders, the mean number of hours per week that they watched television was 19.6 with a standard deviation of 5.8 hours.

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Question 120 Chỉnh sửa
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Let X be a random variable has the following uniform density function f(x) = 0.1 when 0< x < 10. What is the probability that the random variable X has a value greater than 5.3?

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Question 121 Chỉnh sửa
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Jared was working on a project to look at global warming and accessed an Internet site where he captured average global surface temperatures from 1866. Which of the four methods of data collection was he using?

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Question 122 Chỉnh sửa
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If you were constructing a 99% confidence interval of the population mean based on a sample of n=25 where the standard deviation of the sample s = 0.05, the critical value of t will be
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Question 123 Chỉnh sửa
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Suppose that P(A|B) = 0.3 and P(B) = 0.4. Determine P(A' and B).

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Question 124 Chỉnh sửa
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The diameter of ball bearings produced in a manufacturing process can be explained using a uniform distribution over the interval 4.5 to 6.5 millimeters. What is the probability that a randomly selected ball bearing has a diameter greater than 5.2 millimeters?
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Question 125 Chỉnh sửa
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Suppose that $$X$$ has the probability density function $$f(x)=1.5x^2$$ for $$-1
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Question 126 Chỉnh sửa
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Two white mice mate. The male has both a white and a black fur-color gene. The female has only white fur-color genes. The fur color of the offspring depends on the pairs of fur-color genes that they receive. Assume that neither the white nor the black gene dominates. List the possible outcomes. W = white and B = black

Create the sample space of possible outcomes.

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Question 127 Chỉnh sửa
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The diameters of ball bearings produced in a manufacturing process can be described using a uniform distribution over the interval 8.5 to 10.5 millimeters. What is the probability that a randomly selected ball bearing has a diameter greater than 9.2 millimeters?

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Question 128 Chỉnh sửa
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A cereal company claims that the mean weight of the cereal in its packets is at least 14 oz. Assuming that a hypothesis test of the claim has been conducted and that the conclusion is to reject the null hypothesis, state the conclusion in nontechnical terms.

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Question 129 Chỉnh sửa
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Flip a coin three times, create the sample space of possible outcomes.

 

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Question 130 Chỉnh sửa
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Find the standard deviation for the given probability distribution.

x

0

1

2

3

4

P(x)

0.37

0.05

0.13

0.25

0.20


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Question 131 Chỉnh sửa
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The amount of corn chips dispensed into a 20-ounce bag by the dispensing machine has been identified at possessing a normal distribution with a mean of 20.5 ounces and a standard deviation of 0.2-ounce. Suppose 100 bags of chips were randomly selected from this dispensing machine. Find the probability that the sample mean weight of these 100 bags exceeded 20.6 ounces.

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Question 132 Chỉnh sửa
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The length of time it takes college students to find a parking spot in the library parking lot follows a normal distribution with a mean of 4.0 minutes and a standard deviation of 1 minute. Find the probability that a randomly selected college student will take between 2.5 and 5.0 minutes to find a parking spot in the library lot.
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Question 133 Chỉnh sửa
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A store manager kept track of the number of newspapers sold each week over a seven-week period. The results are shown below:
95,  38,  221, 122, 258, 237, 233.
Find the median number of newspapers sold
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Question 134 Chỉnh sửa
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A psychologist claims that more than 3 percent of the population suffers from professional problems due to extreme shyness. Assume that a hypothesis test of the given claim will be conducted. Identify the type II error for the test.

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Question 135 Chỉnh sửa
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According to police sources a car with a certain protection system will be recovered 87% of the time. Find the probability that 4 of 7 stolen cars will be recovered.
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Question 136 Chỉnh sửa
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If X is a normal random variable with μ = 50 and σ = 6, then the probability that X is not between 44 and 56 is
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Question 137 Chỉnh sửa
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An entomologist writes an article in a scientific journal which claims that fewer than 16 in ten thousand male fireflies are unable to produce light due to a genetic mutation. Assume that a hypothesis test of the given claim will be conducted. Identify the type I error for the test.

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Question 138 Chỉnh sửa
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Those methods involving the collection, presentation, and characterization of a set of data in order to properly describe the various features of that set of data are called
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Question 139 Chỉnh sửa
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The following table shows the political affiliation of voters in one city and their positions on stronger gun control laws.

Favor
Oppose
Republican
0.11
0.27
Democrat
0.25
0.16
Other
0.15
0.06

What is the probability that a Democrat opposes stronger gun control laws?
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Question 140 Chỉnh sửa
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The distances traveled (in miles) to 7 different swim meets are given below:
12,  18,  31,  46,  69,  71,  85.
Find the median distance traveled.
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Question 141 Chỉnh sửa
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We have created a 95% confidence interval for $$\mu$$ with the result (10, 15). What decision will we make if we test $$H_0: \mu =16$$ versus $$H_1: \mu
eq 16$$ at $$\alpha= 0.05$$?
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Question 142 Chỉnh sửa
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A researcher claims that 62% of voters favor gun control.Express the null hypothesis H0 and the alternative hypothesis H1 in symbolic form.

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Question 143 Chỉnh sửa
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In a binomial distribution with 10 trials, which of the following is true?
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Question 144 Chỉnh sửa
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If a random variable has the normal distribution with μ = 30 and σ = 5, find the probability that it will take on the value between 31 and 35.

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Question 145 Chỉnh sửa
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To determine the difference , if any, between two brands of radial tires, 12 tires of each brand are tested. Assume that the lifetimes of both brands of tires come from the same normal distribution N(m, 33002). The distribution of the difference of the sample mean $$\overline{X}$$ - $$\overline{Y}.$$

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Question 146 Chỉnh sửa
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Assume that the data has a normal distribution and the number of observations is greater than fifty. Find the critical z value used to test a null hypothesis.


α = 0.05 for a two-tailed test.

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Question 147 Chỉnh sửa
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Assume that z scores are normally distributed with a mean of 0 and a standard deviation of 1. If P(-a < Z < a) = 0.4314, find a.
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Question 148 Chỉnh sửa
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Suppose X is a uniform random variable over the interval [40, 70]. Find the standard deviation of X.

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Question 149 Chỉnh sửa
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Let X represent the amount of time it takes a student to park in the library parking lot at the university. If we know that the distribution of parking times can be modeled using an exponential distribution with a mean of 4 minutes, find the probability that it will take a randomly selected student more than 10 minutes to park in the library lot.
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Question 150 Chỉnh sửa
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If two balanced die are rolled, the possible outcomes can be represented as follows.

(1, 1) (2, 1) (3, 1) (4, 1) (5, 1) (6, 1)
(1, 2) (2, 2) (3, 2) (4, 2) (5, 2) (6, 2)
(1, 3) (2, 3) (3, 3) (4, 3) (5, 3) (6, 3)
(1, 4) (2, 4) (3, 4) (4, 4) (5, 4) (6, 4)
(1, 5) (2, 5) (3, 5) (4, 5) (5, 5) (6, 5)
(1, 6) (2, 6) (3, 6) (4, 6) (5, 6) (6, 6)

Determine the probability that the sum of the dice is 4 or 12.
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Question 151 Chỉnh sửa
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According to the Center for Disease Control, 41.5% of babies born in the U.S. in 2004 were still being breastfed at 6 months of age. If 4 children who were born in the U.S. in 2004 are randomly selected, what is the probability that none of them were breastfed for at least 6 months?
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Question 152 Chỉnh sửa
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When considering area under the standard normal curve, decide whether the area between z = -1.5 and z = 1.1 is bigger than, smaller than, or equal to the area between z = -1.1 and z = 1.5.
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Question 153 Chỉnh sửa
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A polltaker asked graduating college seniors how many times they had given blood in the last year. The results of the survey are given below. The random variable x represents the number of times a person gave blood and P(x) represents the probability of selecting a graduating college who had given blood that percent of the time. What is the standard deviation for the number of times a person gave blood based on this poll?

x

0

1

2

3

4

5

6

P(x)

0.30

0.25

0.20

0.12

0.07

0.04

0.02

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Question 154 Chỉnh sửa
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Let $$X$$ be uniformly distributed over [0, 1]. Calculate $$E[X^3]$$.
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Question 155 Chỉnh sửa
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The lifetimes of light bulbs of a particular type are normally distributed with a mean of 360 hours and a standard deviation of 5 hours. What percentage of the bulbs have lifetimes that lie within 1 standard deviation of the mean?
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Question 156 Chỉnh sửa
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The breakdown of workers in a particular state according to their political affiliation and type of job held is shown here. Suppose a worker is selected at random within the state and the worker's political affiliation and type of job are noted.
Political Affiliation


Given the worker is a Democrat, what is the probability that the worker is in a white collar job.
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Question 157 Chỉnh sửa
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The age distribution of students at a community college is given below.
Age (years)
Number of students
Under 21
409
21-24
404
25-28
276
29-32
155
33-36
97
37-40
63
Over 40
86

A student from the community college is selected at random. Find the probability that the student is 21 years or over. Give your answer as a decimal rounded to three decimal places.
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Question 158 Chỉnh sửa
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The lengths of human pregnancies are normally distributed with a mean of 268 days and a standard deviation of 15 days. What is the probability that a pregnancy lasts at least 300 days?
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Question 159 Chỉnh sửa
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The probability that a house in an urban area will be burglarized is 2%. If 29 houses are randomly selected, what is the probability that none of the houses will be burglarized?
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Question 160 Chỉnh sửa
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The diameters of pencils produced by a certain machine are normally distributed with a mean of 0.30 inches and a standard deviation of 0.01 inches. What is the probability that the diameter of a randomly selected pencil will be less than 0.285 inches?
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Question 161 Chỉnh sửa
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Based on the scores 1, 9, 3, 6, 1, 2, 6, 2, 2, and 8, a score of 4 is the
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Question 162 Chỉnh sửa
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Compute the critical value $$z_{\alpha/2}$$ that corresponds to a 94% level of confidence.

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Question 163 Chỉnh sửa
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For two events A and B, P(A) = 0.8, P(B) = 0.2, and P(A and B) = 0.16. It follows that A and B are

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Question 164 Chỉnh sửa
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A test consists of 10 true/false questions. To pass the test a student must answer at least 7 questions correctly. If a student guesses on each question, what is the probability that the student will pass the test?
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Question 165 Chỉnh sửa
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Find the mean of the data summarized in the given frequency distribution.
Daily Low Temperature (F)Frequency
35-391
40-443
45-495
50-5411
55-597
60-647
65-691
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Question 166 Chỉnh sửa
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A machine is set to pump cleanser into a process at the rate of 10 gallons per minute. Upon inspection, it is learned that the machine actually pumps cleanser at a rate described by the uniform distribution over the interval 9.5 to 13.5 gallons per minute. Find the variance of the distribution.

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Question 167 Chỉnh sửa
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Friskie is having her fifth litter. The prior litters have either been three normal pups or two normal pups and a runt. Assume the probability of either outcome is 50%.

Create the sample space of possible outcomes.

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Question 168 Chỉnh sửa
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According to a survey of American households, the probability that the residents own 2 cars if annual household income is over $25,000 is 80%. Of the households surveyed, 60% had incomes over $25,000 and 70% had 2 cars. The probability that annual household income is over $25,000 if the residents of a household own 2 cars is:
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Question 169 Chỉnh sửa
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According to a survey of American households, the probability that the residents own 2 cars if annual household income is over $25,000 is 80%. Of the households surveyed, 60% had incomes over $25,000 and 70% had 2 cars. The probability that the residents of a household do not own 2 cars and have an income over $25,000 a year is:
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Question 170 Chỉnh sửa
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Assume that the heights of men are normally distributed. A random sample of 16 men have a mean height of 67.5 inches and a standard deviation of 3.2 inches. Construct a 99% confidence interval for the population standard deviation, $$\sigma.$$

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Question 171 Chỉnh sửa
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When considering area under the standard normal curve, decide whether the area between z = 3 and z = -3 is bigger than, smaller than, or equal to the area between z = 2.7 and z = 2.9.
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Question 172 Chỉnh sửa
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Find the standard deviation for the binomial distribution which has the stated values of n and p. Round your answer to the nearest hundredth.

n = 2661; p = 0.63
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Question 173 Chỉnh sửa
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 Survey responses of temperatures of the ocean at various depths. which type of data is?

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Question 174 Chỉnh sửa
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Let X be a uniform random variable  over the interval [1, 9] . What is the probability that the random variable X has a value less than 6?

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Question 175 Chỉnh sửa
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Find the variance for the given sample data
53   52   75   62   68   58   49   49
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Question 176 Chỉnh sửa
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At a computer manufacturing company, the actual size of computer chips is normally distributed with a mean of 1 centimeter and a standard deviation of 0.1 centimeter. A random sample of 12 computer chips is taken. What is the standard error for the sample mean?
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Question 177 Chỉnh sửa
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Find z if the normal curve area to the right of z is 0.8997.

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Question 178 Chỉnh sửa
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The heights of a group of professional basketball players are summarized in the frequency distribution below. Find the mean height. Round your answer to one decimal place.
mc011-1.jpg
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Question 179 Chỉnh sửa
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Assume that blood pressure readings are normally distributed with a mean of 124 and a standard deviation of 6.4. If 64 people are randomly selected, find the probability that their mean blood pressure will be less than 126.

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Question 180 Chỉnh sửa
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The probability of winning a certain lottery is 1/51949. For people who play 560 times, find the standard deviation for the random variable X, the number of wins.
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Question 181 Chỉnh sửa
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The mean diameter of marbles manufactured at a particular toy factory is 0.850 cm with a standard deviation of 0.010cm. What is the probability of selecting a random sample of 100 marbles that has a mean diameter greater than 0.851 cm?

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Question 182 Chỉnh sửa
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Suppose that a number of miles that a car can run before its battery wears out is exponentially distributed with an average value of 10000 miles. If a person desires to take a 5000-mile trip, what is the probability that she will be able to complete her trip without having to replace her car battery?
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Question 183 Chỉnh sửa
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The distribution of B.A. degrees conferred by a local college is listed below, by major.
Major
Frequency
Engineering
868
English
2073
Mathematics
2164
Chemistry
318
Physics
856
Liberal Arts
1358
Business
1676

What is the probability that a randomly selected degree is not in Mathematics?
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Question 184 Chỉnh sửa
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Assume that X has a normal distribution with the mean is μ = 15.2 and the standard deviation is σ = 0.9. Find the probability that X is between 14.3 and 16.1.
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Question 185 Chỉnh sửa
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Let Z is a standard normal variable, find the probability that Z lies between -1.10 and -0.36.
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Question 186 Chỉnh sửa
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According to the 2003 National Survey on Drug Use and Health, 54.3% of males have never used marijuana. Based on this percentage, what is the expected number of males who have used marijuana for samples of size 100?
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Question 187 Chỉnh sửa
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It has been found that 40% of the employees who complete a sequence of executive seminars go on to become vice presidents. Assume that 10 graduates of the program are randomly selected, find the probability that from two to four become vice presidents.

(Note: please give the answer as a real number accurate to 4 decimal places after the decimal point.)

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#Thực hiệnĐáp ánTimeRaw scoreĐiểm
1Điểm22:02:23 on 3/04/1100
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Question 188 Chỉnh sửa
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Sixty-five percent of men consider themselves knowledgeable football fans. If 13 men are randomly selected, find the probability that exactly five of them will consider themselves knowledgeable fans.
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Question 189 Chỉnh sửa
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The number of ounces of soda that a vending machine dispenses per cup is normally distributed with a mean of 12 ounces and a standard deviation of 4 ounces. Find the probability that more than 16 ounces is dispensed in a cup.

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Question 190 Chỉnh sửa
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Find the mean for the binomial distribution which has the stated values of n and p. Round answer to the nearest tenth.

n = 33; p = 0.2
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Question 191 Chỉnh sửa
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The weights of the fish in a certain lake are normally distributed with a mean of 15 lb and a standard deviation of 6. If 4 fish are randomly selected, what is the probability that the mean weight will be between 12.6 and 18.6 lb.

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Question 192 Chỉnh sửa
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The time (in years) until the first critical-part failure for a certain car is exponentially distributed with a mean of 3.4 years. Find the probability that the time until the first critical-part failure is 5 years or more.

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Question 193 Chỉnh sửa
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At a California college, 22% of students speak Spanish, 5% speak French, and 3% speak both languages. What is the probability that a student chosen at random from the college speaks Spanish but not French?
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Question 194 Chỉnh sửa
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Assume that the heights of women are normally distributed. A random sample of 20 women have a mean height of 62.5 inches and a standard deviation of 2.5 inches. Construct a 98% confidence interval for the population variance, $$\sigma^2.$$

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Question 195 Chỉnh sửa
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Construct the boxplot for the given data below:
3,  3,  5,  6,  4,  9,  8,  9,  6.
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Question 196 Chỉnh sửa
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A die is rolled 10 times and the number of times that two shows on the up face is counted. If this experiment is repeated many times, find the mean for the random variable X, the number of twos thrown out of ten tosses.
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Question 197 Chỉnh sửa
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Find the critical value or values of x2 based on the given information.


H1: σ ≠ 9.3

n = 28

α = 0.05

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Question 198 Chỉnh sửa
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A population of Australian Koala bears has a mean height of 20 inches and a standard deviation of 4 inches. You plan to choose a sample of 64 bears at random. What is the probability of a sample mean between 20 and 21.

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Question 199 Chỉnh sửa
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Assume that a researcher randomly selects 14 newborn babies and counts the number of girls selected, X. The probabilities corresponding to the 14 possible values of x are summarized in the given table. Answer the question using the following table.

X(girls)01234567891011121314
P(X)0.0000.0010.0060.0220.0610.1220.1830.2090.1830.1220.0610.0220.0060.0010.000

 Find the probability of selecting 9 or more girls.

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Question 200 Chỉnh sửa
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The random variable X represents the number of girls in a family of three children. Assuming that boys and girls are equally likely, find the mean and standard deviation for the random variable X.
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Question 201 Chỉnh sửa
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The amount of soda a dispensing machine pours into a 12 ounce can of soda follows a normal distribution with a mean of 12.27 ounces and a standard deviation of 0.18 ounce. The cans only hold 12.45 ounces of soda. Every can that has more than 12.45 ounces of soda poured into it causes a spill and the can needs to go through a special cleaning process before it can be sold. What is the probability a randomly selected can will need to go through this process?
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Question 202 Chỉnh sửa
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An electrical firm manufactures a certain type of light bulb that has a mean light of 1,800 hours and a standard deviation of 200 hours. Find the probability that a random sample of 100 bulbs will have an average life of more than 1,825 hours.

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Question 203 Chỉnh sửa
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A psychologist claims that more than 6.3 percent of the population suffers from professional problems due to extreme shyness. Use p, the true percentage of the population that suffers from extreme shyness. Express the null hypothesis H0 and the alternative hypothesis H1 in symbolic form.

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Question 204 Chỉnh sửa
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A major videocassette rental chain is considering opening a new store in an area that currently does not have any such stores. The chain will open if there is evidence that more than 25% households in the area are equipped with videocassette recorders (VCRs). It conducts a telephone poll of 300 randomly selected households in the area and finds that 96 have VCRs. The value of the test statistic in this problem is approximately equal to
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Question 205 Chỉnh sửa
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Which of the following is a discrete quantitative variable?
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Question 206 Chỉnh sửa
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Suppose that the probability that a particular brand of light bulb fails before 900 hours of use is 0.2. If you purchase 3 of these bulbs, what is the probability that at least one of them lasts 900 hours or more?
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Question 207 Chỉnh sửa
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Determine whether the given conditions justify testing a claim about a population mean μ.

The sample size is n = 49, σ = 12.3, and the original population is not normally distributed.

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Question 208 Chỉnh sửa
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Which of the following is a continuous quantitative variable?
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Question 209 Chỉnh sửa
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Determine whether the hypothesis test involves a sampling distribution of means that is a normal distribution, Student t distribution, or neither.


Claim: μ = 78. Sample data: n = 24, $$\overline{x} = 101,$$ s = 15.3. The sample data appear to come from a population with a distribution that is very far from normal, and σ is unknown.

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Question 210 Chỉnh sửa
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A supermarket manager has determined that the amount of time customers spend in the supermarket is approximately normally distributed with a mean of 45 minutes and a standard deviation of 6 minutes. Find the number of minutes, m, for which the probability that a customer spends less than m minutes in the supermarket is 0.10.

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Question 211 Chỉnh sửa
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If you flip a coin three times, the possible outcomes are HHH HHT HTH HTT THH THT TTH TTT. What is the probability of getting at least one head?
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Question 212 Chỉnh sửa
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The owner of a football team claims that the average attendance at games is over 60,000, and he is therefore justified in moving the team to a city with a larger stadium. Assume that a hypothesis test of the given claim will be conducted. Identify the type II error for the test.

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Question 213 Chỉnh sửa
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On a 10-question multiple choice test , each question has four possible answers, one of which is correct. For students who guess at all answers, find the mean for the random variable X, the number of correct answers.
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Question 214 Chỉnh sửa
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An economist is interested in studying the incomes of consumers in a particular region. The population standard deviation is known to be $1000. A random sample of 50 individuals resulted in an average income of $15000. What is the width of the 90% confidence interval?

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Question 215 Chỉnh sửa
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Assume that the data has a normal distribution and the number of observations is greater than fifty. Find the critical z value used to test a null hypothesis.


α = 0.09 for a right-tailed test.

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Question 216 Chỉnh sửa
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 Which of the following statements is false

i) If X1, X2,…,Xn is a random sample of size n, the sample standard deviation S is not a statistic.
ii) The probability distribution of a statistic is called a sampling distribution.
iii) A statistic is any function of the observations in a random sample.
iv) The sampling distribution of a statistic does not depend on the distribution of the population.
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Question 217 Chỉnh sửa
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An entomologist writes an article in a scientific journal which claims that fewer than 11 in ten thousand male fireflies are unable to produce light due to a genetic mutation. Use the parameter p, the true proportion of fireflies unable to produce light. Express the null hypothesis H0 and the alternative hypothesis H1 in symbolic form.

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Question 218 Chỉnh sửa
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According to a CNN poll taken in February of 2008, 67% of respondents disapproved of the overall job that President Bush was doing. Based on this poll, for samples of size 200, what is the mean number of American adults who disapprove of the overall job that President Bush is doing?
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Question 219 Chỉnh sửa
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A university dean is interested in determining the proportion of students who receive some sort of financial aid. Rather than examine the records for all students, the dean randomly selects 200 students and finds that 118 of them are receiving financial aid. Use a 95% confidence interval to estimate the true proportion of students on financial aid.

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Question 220 Chỉnh sửa
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The peak shopping time at home improvement store is between 8-11:00 am on Saturday mornings. Management at the home improvement store randomly selected 150 customers last Saturday morning and decided to observe their shopping habits. They recorded the number of items that a sapmle of the customers purchased as well as the total time the customers spent in the store. Identify the types of variables recorded by the home improvement store.
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Question 221 Chỉnh sửa
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An airline reports that it has been experiencing a 15% rate of no-shows on advanced reservations. Among 150 advanced reservations, find the probability that there will be fewer than 20 no-shows.
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Question 222 Chỉnh sửa
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The name of each contestant is written on a separate card, the cards are placed in a bag, and     three names are picked from the bag. Identify which of these types of sampling is used: Stratified, systematic, cluster, random.

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Question 223 Chỉnh sửa
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A skeptical paranormal researcher claims that the proportion of Americans that have seen a UFO, p, is less than 1 in every one thousand. Assume that a hypothesis test of the given claim will be conducted. Identify the type II error for the test.

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Question 224 Chỉnh sửa
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A random sample of 40 students has a mean annual earnings of $3120 and a population standard deviation of $677. Construct the confidence interval for the population mean, μ. Use a 95% confidence level.

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Question 225 Chỉnh sửa
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An economist is interested in studying the incomes of consumers in a particular region. The normally population standard deviation is known to be $1000. What total sample size would the economist need to use for a 95% confidence interval if the width of the interval should not be more than $100? Let $$z_{0.025}=1.96; z_{0.05}=1.65$$.
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Question 226 Chỉnh sửa
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The time (in years) until the first critical-part failure for a certain car is exponentially distributed with a mean of 3.4 years. Find the probability that the time until the first critical-part failure is less than 1 year.

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Question 227 Chỉnh sửa
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A study of  the amount of time it take a mechanic to rebuild the transmission for a 1992 Chevrolet Cavalier shows that the mean is 8.4 hours and the standard deviation is 1.8 hours. If 40 mechanics are randomly selected, find the probability that their mean rebuild time exceeds 8.7 hours.
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Question 228 Chỉnh sửa
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Suppose x is a uniform random variable over [10,90]. Find the probability that a randomly selected observation exceeds 26.
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Question 229 Chỉnh sửa
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A university dean is interested in determining the proportion of students who receive some sort of financial aid. Rather than examine the records for all students, the dean randomly selects 200 students and finds that 118 of them are receiving financial aid. Use a 90\% confidence interval to estimate the true proportion of students who receive financial aid. Let $$z_{0.1}=1.28;z_{0.05}=1.65$$.
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Question 230 Chỉnh sửa
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To determine the mean of a binomial distribution, it is necessary to know the number of successes involved in the problem.
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Question 231 Chỉnh sửa
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Which of the following is always true for a normal distribution?
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Question 232 Chỉnh sửa
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Find the normal-curve area between z = -1.48 and z = 0.

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Question 233 Chỉnh sửa
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Brandon and Samantha each carry a bag containing a banana, a chocolate bar, and a licorice stick. Simultaneously, they take out a single food item and consume it. The possible pairs of food items that Brandon and Samantha consumed are as follows.

chocolate bar - chocolate bar
licorice stick - chocolate bar
banana - banana
chocolate bar - licorice stick
licorice stick - licorice stick
chocolate bar - banana
banana - licorice stick
licorice stick - banana
banana - chocolate bar

Find the probability that at least one chocolate bar was eaten.
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Question 234 Chỉnh sửa
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A study of 1000 randomly selected flights of a major airline showed that 782 of the flights arrived on time. What is the probability of a flight arriving on time?
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Question 235 Chỉnh sửa
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Assume that the weights of quarters are normally distributed with a mean of 5.67 g and a standard deviation 0.070 g. A vending machine will only accept coins weighing between 5.48 g and 5.82 g. What percentage of legal quarters will be rejected?
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Question 236 Chỉnh sửa
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In a recent survey, 80% of the community favored building a police substation in their neighborhood. If 15 citizens are chosen, what is the mean number favoring the substation?
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Question 237 Chỉnh sửa
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The tread life of a particular brand of tire is a random variable best described by a normal distribution with a mean of 60,000 miles and a standard deviation of 1900 miles. What is the probability a certain tire of this brand will last between 56,010 miles and 56,580 miles?
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Question 238 Chỉnh sửa
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According to a 2007 report published by the National Center on Addiction and Substance Abuse at Columbia University, 59% of teens have family dinners five or more times a week, 13% of teens have used marijuana and the proportion of teens who have family dinners 5 or more times a week or use marijuana is 0.64. What is the probability that a teen has family dinners five or more times a week and uses marijuana?

Hint. Use the addition rules.

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Question 239 Chỉnh sửa
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A percentage distribution is given below for the size of families in one U.S. city.
Size
Percentage
2
45.1
3
22.2
4
19.7
5
8.0
6
3.1
7+
1.9

A family is selected at random. Find the probability that the size of the family is less than 6. Round your result to three decimal places.
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Question 240 Chỉnh sửa
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The principal of a middle school claims that test scores of the seventh-graders at her school vary less than the test scores of seventh-graders at a neighboring school, which have variation described by σ  = 14.7. Express the null hypothesis H0 and the alternative hypothesis H1 in symbolic form.

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Question 241 Chỉnh sửa
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To calculate the probability of obtaining three aces in eight draws of a card with replacement from an ordinary deck, we would use the
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Question 242 Chỉnh sửa
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The outcome of an experiment is the number of resulting heads when a nickel and a dime are flipped simultaneously. What is the sample space for this experiment?

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Question 243 Chỉnh sửa
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If we are using the normal approximation to determine the probability of at most 28 successes in a binomial distribution P(x ≤ 28) the normal distribution probability that is used to make the estimate is
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Question 244 Chỉnh sửa
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The use of the Poisson distribution requires a value n which indicates a definite number of independent trials.
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Question 245 Chỉnh sửa
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The process of using sample statistics to draw conclusions about true population parameters is called
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Question 246 Chỉnh sửa
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In 2006, the percent of the voting-age population that was registered to vote for the 50 states and the District of Columbia had a mean of 65% with a standard deviation of 7.1. Assuming that the distribution is normal, what percentage of states had between 50 and 70 percent of it's voting-age population who were registered to vote?
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Question 247 Chỉnh sửa
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A stock analyst compares the relationship between stock prices and earnings per share to help him select a stock for investment. What type of the description is?

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Question 248 Chỉnh sửa
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According to a college survey, 22% of all students work full time. Find the mean for the random variable X, the number of students who work full time in samples of size 16.
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Question 249 Chỉnh sửa
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The following table contains the probability distribution for X = the number of traffic accidents reported in a day in Hanoi.
X 0 1 2 3 4 5
P(X) 0.10 0.20 0.45 0.15 0.05 0.05
The probability of more than 2 accidents is
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Question 250 Chỉnh sửa
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A Type II error is committed when
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Question 251 Chỉnh sửa
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Use the given information to find the P-value.

The test statistic in a right-tailed test is z = 0.52.
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Question 252 Chỉnh sửa
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A company had 80 employees whose salaries are summarized in the frequency distribution below. Find the mean salary.

mc020-1.jpg
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Question 253 Chỉnh sửa
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According to the Center for Disease Control, in 2004, 65.7% of all adults between the ages of 18 and 44 were considered current drinkers. Based on this estimate, if two randomly selected adults between the ages of 18 and 44 are selected, what is the probability that at least one is a current drinker?
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Question 254 Chỉnh sửa
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An article a Florida newspaper reported on the topics that teenagers most want to discuss with their parents. The findings, the results of a poll, showed that 46% would like more discussion about the family's financial situation, 37% would like to talk about school, and 30% would like to talk about religion. These and other percentages were based on a national sampling of 549 teenagers. Estimate the proportion of all teenagers who want more family discussions about school. Use a 99% confidence level.

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Question 255 Chỉnh sửa
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Which of the following is not true of statistics?

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Question 256 Chỉnh sửa
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A group of 40 bowlers showed that their average score was 192 with a population standard deviation of 8. Find the 95% confidence interval of the mean score of all bowlers.
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Question 257 Chỉnh sửa
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The number of ounces of soda that a vending machine dispenses per cup is normally distributed with a mean of 12 ounces and a standard deviation of 4 ounces. Find the probability that between 15 and 18 ounces are dispensed in a cup.

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Question 258 Chỉnh sửa
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Let X be a uniform random variable over the interval [0, 8] . What is the probability that the random variable X has a value greater than 3?

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Question 259 Chỉnh sửa
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A confidence interval was used to estimate the proportion of statistics students that are female. A random sample of 72 statistics students generated the following 90% confidence interval: (0.438, 0.642). Using the information above, what total size sample would be necessary if we wanted to estimate the true proportion to within 0.08 using 95% confidence?
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Question 260 Chỉnh sửa
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The area to the right of z = 1.0 is equal to
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Question 261 Chỉnh sửa
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Use the given information to find the P-value.

The test statistic in a left-tailed test is z = -2.05.
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Question 262 Chỉnh sửa
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Suppose that11% of people are left handed. If 6 people are selected at random, what is the probability that exactly 2 of them are left handed?
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Question 263 Chỉnh sửa
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Suppose that the random variable X has an exponential distribution with λ = 1.5. Find the mean and standard deviation of X.

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Question 264 Chỉnh sửa
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A survey of senior citizens at a doctor's office shows that 52% take blood pressure-lowering medication, 43% take cholesterol-lowering medication, and 5% take both medications. What is the probability that a senior citizen takes either blood pressure-lowering or cholesterol-lowering medication?
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Question 265 Chỉnh sửa
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The diameters of bolts produced by a certain machine are normally distributed with a mean of 0.30 inches and a standard deviation of 0.01 inches. What percentage of bolts will have a diameter greater than 0.32 inches?
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Question 266 Chỉnh sửa
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Assume that the heights of men are normally distributed. A random sample of 16 men have a mean height of 67.5 inches and a standard deviation of 2.2 inches. Construct a 99% confidence interval for the population standard deviation. Let $$\chi_{0.005,15}^2=32.8;\chi_{0.995,15}^2=4.6$$.
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Question 267 Chỉnh sửa
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If Z is a standard normal variable, find the the probability that Z is less than 1.13.
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Question 268 Chỉnh sửa
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For women aged 18-24, systolic blood pressures ( in mm Hg) are normally distributed with a mean of 114.8 and a standard deviation of 13.1. If 23 women aged 18-24 are randomly selected, find the probability that their mean systolic blood pressures is between 119 and 122.

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Question 269 Chỉnh sửa
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According to a survey of American households, the probability that the residents own 2 cars if annual household income is over $25,000 is 80%. Of the households surveyed, 60% had incomes over $25,000 and 70% had 2 cars. The probability that the residents of a household own 2 cars and have an income over $25,000 a year is:
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Question 270 Chỉnh sửa
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A nurse measured the blood pressure of each person who visited her clinic. Following is a relative-frequence histogram for the systolic blood pressure readings for those people aged between 25 and 40. The blood pressure reading were given to the nearest whole number. Approximately what percentage of the people aged 25-40 had a systolic blood pressure reading between 110 and 119 inclusive?
mc001-1.jpg

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Question 271 Chỉnh sửa
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Assume that a procedure yields a binomial distribution with a trial repeated n times. Use the binomial probability formula to find the probability of x successes given the probability p of success on a single trial.

n = 64, x = 3, p = 0.04
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Question 272 Chỉnh sửa
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Private colleges and universities rely on money contributed by individuals and corporations for their operating expenses. Much of this money is put into a fund called an endowment, and the college spends only the interest earned by the fund. A recent survey of 8 private colleges in Vietnam revealed the following endowments (in millions of dollars) 60.2, 47.0, 235.1, 490.0, 122.6, 177.5, 95.4, and 220.0. What value will be used as the point estimate for the mean endowment of all private colleges in Vietnam?
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Question 273 Chỉnh sửa
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The number of 113 calls in Hanoi, has a Poisson distribution with a mean of 10 calls a day. The probability of seven 113 calls in a day is
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Question 274 Chỉnh sửa
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Find the normal-curve area between z = -2 and z = -1.

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Question 275 Chỉnh sửa
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Assume that z scores are normally distributed with a mean of 0 and a standard deviation of 1. If P(0.2 < Z < a) = 0.2314, find a.
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Question 276 Chỉnh sửa
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If a random variable has the normal distribution with μ = 30 and σ = 5, find the probability that it will take on the value between 24 and 28.

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Question 277 Chỉnh sửa
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A 99% confidence interval estimate can be interpreted to mean that
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Question 278 Chỉnh sửa
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In 2006, the General Social Survey asked 4,491 respondents how often they attended religious services. The responses were as follows:

FrequencyNumber of respondents
Never1020
Less than once a year302
Once a year571
Several times a year502
Once a month308
Two-three times a month380
Nearly every week240
Every week839
More than once a week329



What is the probability that a randomly selected respondent attended religious services more than once a year?

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Question 279 Chỉnh sửa
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Find z if the normal curve area between 0 and z is 0.4756.

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Question 280 Chỉnh sửa
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The paired data below consist of the test scores of 6 randomly selected students and the number of hours they studied for the test.
Hours 5 10 4 6 10 9
Score 4 8 3 6 9 8
$$
Find the value of the linear correlation coefficient $$r$$.
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Question 281 Chỉnh sửa
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A catalog company that receives the majority of its orders by telephone conducted a study to determine how long customers were willing to wait on hold before ordering a product. The length of time was found to be a random variable best approximated by an exponential distribution with a mean equal to 3 minutes. Find the waiting time at which only 10% of the customers will continue to hold.
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Question 282 Chỉnh sửa
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Construct a 95% confidence interval for the population mean, μ. Assume the population has a normal distribution. A sample of 25 randomly selected students has a mean test score of 81.5 with a standard deviation of 10.2.

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Question 283 Chỉnh sửa
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Patients arriving at an outpatient clinic follow an exponential distribution at a rate of 15 patients per hour. What is the probability that a randomly chosen arrival to be less than 15 minutes?

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Question 284 Chỉnh sửa
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A student randomly selects 10 CDs at a store. The mean is $8.75 with a standard deviation of $1.50. Construct a 95% confidence interval for the population standard deviation, $$\sigma.$$ Assume the data are normally distributed.

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Question 285 Chỉnh sửa
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If $$n = 10$$ and $$p = 0.70$$, then the standard deviation of the binomial distribution is
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Question 286 Chỉnh sửa
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A telemarketer found that there was a 1% chance of a sale from his phone solicitations. Find the probability of getting 5 or more sales for 1000 telephone calls.
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Question 287 Chỉnh sửa
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Which of the following cannot be a probability?
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Question 288 Chỉnh sửa
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Find the variance of the given data. Round your answer to one more decimals than the original data.
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Question 289 Chỉnh sửa
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In 2005, the property crime rates (per 100,000 residents) for the 50 states and the District of Columbia had a mean of 3377.2 and a standard deviation of 847.4. Assuming the distribution of property crime rates is normal, what percentage of the states had property crime rates between 2360 and 4055?
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Question 290 Chỉnh sửa
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According to the U.S. census, in 2005 21% of homicide vic