500 câu trắc nghiệm Kinh tế lượng – 5B

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
Identify the probability of each sample, and describe the sampling distribution of the sample means.
11) The number of books sold over the course of the four-day book fair were 196, 195, 264, and 60. Assume that samples of size 2 are randomly selected with replacement from this population of four values.
○ 0/16; 1/16; 1/8; 0/16; 1/16; 1/8; 1/16; 0/16; 1/8; 1/16; 1/16; 1/8; 1/16; 0/16; 1/8; 1/16
○ 1/2; 1/16; 1/4; 1/16; 1/4; 1/16; 1/2; 1/16; 1/4; 1/16; 1/2; 1/16; 1/4; 1/16; 1/2; 1/16
○ 1/16; 1/8; 0/16; 1/16; 1/8; 0/16; 1/16; 1/8; 0/16; 1/16; 1/8; 0/16; 1/16; 1/8; 0/16; 1/16
● 1/16; 1/16; 1/16; 1/16; 1/16; 1/16; 1/16; 1/16; 1/16; 1/16; 1/16; 1/16; 1/16; 1/16; 1/16; 1/16

Solve the problem.
12) Suppose that replacement times for washing machines are normally distributed with a mean of 9.3 years and a standard deviation of 1.1 years. Find the probability that 70 randomly selected washing machines will have a mean replacement time less than 9.1 years.
○ 0.4357
○ 0.4286
● 0.0643
○ 0.0714

13) A study of the amount of time it takes 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 9.1 hours.
○ 0.0046
○ 0.1285
○ 0.1046
● 0.0069

14) A final exam in Math 160 has a mean of 73 with standard deviation 7.8. If 24 students are randomly selected, find the probability that the mean of their test scores is less than 76.
○ 0.9203
● 0.9699
○ 0.8962
○ 0.0301

Use the continuity correction and describe the region of the normal curve that corresponds to the indicated
binomial probability.
15) The probability that the number of correct answers is between 23 and 60 inclusive
● The area between 22.5 and 60.5
○ The area between 22.5 and 59.5
○ The area between 23.5 and 59.5
○ The area between 23 and 60

For the binomial distribution with the given values for n and p, state whether or not it is suitable to use the normal distribution as an approximation.
16) n = 19 and p = .8
○ Normal approximation is suitable.
● Normal approximation is not suitable.
Estimate the indicated probability by using the normal distribution as an approximation to the binomial distribution.
17) Two percent of hair dryers produced in a certain plant are defective. Estimate the probability that of 10,000 randomly selected hair dryers, exactly 225 are defective.
● 0.0057
○ 0.0051
○ 0.0065
○ 0.0034

Use the normal distribution to approximate the desired probability.
18) A coin is tossed 20 times. A person, who claims to have extrasensory perception, is asked to predict the outcome of each flip in advance. She predicts correctly on 14 tosses. What is the probability of being correct 14 or more times by guessing? Does this probability seem to verify her claim?
○ .4418 , yes
● .0582 , no
○ .0582 , yes
○ .4418 , no

SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
Solve the problem.
19) A normal probability plot is given below for a sample of scores on an aptitude test. Use the plot to assess the normality of scores on this test. Explain your reasoning.

Examine the given data set and determine whether the requirement of a normal distribution is satisfied. Assume that the requirement for a normal distribution is loose in the sense that the population distribution need not be exactly normal, but it must have a distribution which is basically symmetric with only one mode. Explain why you do or do not think that the requirement is satisfied.

Since the normal probability plot is roughly linear, it appears that scores on this test are approximately normally distributed.

20) The ages of 35 students selected randomly from one college are as follows:

21 23 20 24 20
19 20 19 22 32
20 24 26 21 37
23 18 34 25 30
22 24 23 19 28
20 29 21 35 25
20 21 28 22 32

The requirement for normality is not satisfied, since a histogram of the data is not bell shaped. The data does have a single mode; however the histogram is not symmetric, but is skewed to the right.