Suppose that vehicle speeds at an interstate location have a normal distribution with a mean equal to 70 mph and standard deviation equal to 8 mph. What is the z-score for a speed of 64 mph?
a. -6
b. -0.75
c. +0.75
d. +6
Q. 2A 95 confidence interval for the proportion of women that has ever dozed off while driving is 0.07 to 0.14 . For men, a 95 confidence interval for the proportion that has ever dozed off while driving is 0.19 to 0.25 . Assume both intervals were computed using large random samples. What conclusion can be made about the population proportions that have dozed off while driving?
a. It is reasonable to conclude that there is a difference between men and women.
b. It is not reasonable to conclude that there is a difference between men and women.
c. It is reasonable to conclude that there is a difference of 0.05 between men and women.
d. No conclusion is possible because we don't know the margin of error.
Q. 3Assuming a standard normal distribution is appropriate, what is the approximate probability that a z-score is greater than or equal to 2.33? Said another way, what is P(Z 2.33)?
a. 0.99
b. 0.01
c. 0.15
d. 0.25
Q. 4Suppose a 95 confidence interval for the proportion of Americans who exercise regularly is 0.29 to 0.37 . Which one of the following statements is false?
a. It is reasonable to say that more than 25 of Americans exercise regularly.
b. It is reasonable to say that more than 40 of Americans exercise regularly.
c. An acceptable hypothesis is that about 33 of Americans exercise regularly.
d. It is reasonable to say that fewer than 40 of Americans exercise regularly.
Q. 5Find the requested probability for the standard normal random variable Z. What is the probability that Z is between -1.2 and 1.45, P(-1.2 Z 1.45)?
a. 0.0303
b. 0.7740
c. 0.8041
d. 0.8114
Q. 6In a past General Social Survey, a random sample of respondents answered the question Are you a member of any sports groups? Based on the sample data, 95 confidence intervals for the population proportion who would answer yes are 0.215 to 0.365 for people 18 to 23 years old and 0.247 to 0.333 for people 24 to 29 years old. Based on these results, you can reasonably conclude that
a. at least 40 of people aged 18 to 23 years old and people aged 24 to 29 years old belong to sports clubs.
b. there is no conclusive evidence of a difference between the two age groups in the proportions of people belonging to sports clubs.
c. there is conclusive evidence of a difference between the two age groups in the proportions of people belonging to sports clubs.
d. None of the above
Q. 7Find the requested probability for the standard normal random variable Z. What is the probability that Z is between -1 and 1, P(-1 Z 1)?
a. 0.1587
b. 0.3174
c. 0.6826
d. 0.8413
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