500 câu trắc nghiệm Kinh tế lượng – 5A

11) If 9% of the thermometers are rejected because they have readings that are too high, but all other thermometers are acceptable, find the temperature that separates the rejected thermometers from the others.
● 1.34
○ 1.26
○ 1.39
○ 1.45
Assume that X has a normal distribution, and find the indicated probability.
12) The mean is \(\mu \) = 22.0 and the standard deviation is \(\sigma \) = 2.4.
Find the probability that X is between 19.7 and 25.3.
○ 1.0847
○ 0.4107
● 0.7477
○ 0.3370

Solve the problem.
13) 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 70.
○ 0.1.006
● 0.0301
○ 0.9699
○ 0.0278

14) 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 8.1
hours.
● 0.8531
○ 0.7285
○ 0.8457
○ 0.9146

Use the continuity correction and describe the region of the normal curve that corresponds to the indicated
binomial probability.
15) The probability of exactly 56 green marbles
○ The area between 56 and 56.5
○ The area between 55.5 and 57.5
○ The area between 55.5 and 56
● The area between 55.5 and 56.5

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 = 53 and p = .7
○ Normal approximation is not suitable.
● Normal approximation is suitable.

Estimate the indicated probability by using the normal distribution as an approximation to the binomial distribution.
17) A product is manufactured in batches of 120 and the overall rate of defects is 5%. Estimate the probability that a randomly selected batch contains more than 6 defects.
○ 0.4641
○ 0.5871
○ 0.0832
● 0.4168

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 16 tosses. What is the probability of being correct 16 or more times by guessing? Does this probability seem to verify her claim?
○ .4931 , no
○ .0069 , no
○ .4931 , yes
● .0069 , yes
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 the weekly incomes (in dollars) of a sample of engineers in one town. Use the plot to assess the normality of the incomes of engineers in this town. 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 displays curvature, it appears that incomes of engineers in this town
are probably not normally distributed.

20) The heart rates (in beats per minute) of 30 randomly selected students are given below.

78 64 69 75 80
63 70 72 72 68
77 71 74 84 70
62 67 71 69 58
74 70 80 63 88
60 68 69 70 71

The requirement for normality is satisfied since a histogram of the data is roughly bell shaped; it is roughly symmetric with a single mode.