1. A normal distribution is completely determined by:
A ?Its mean and its standard deviation.
B Its mean and its mode.
C Its mean and its median.
D None of the above.
2. The average height of American women is distributed normally, with a mean of 63.5 inches and a standard deviation of 2.5 inches. ??Approximately what percentage of American women are taller than 58.5 inches, but shorter than 68.5 inches?
A ?50%
B ?68%
C ?84%
D ?95%
3. The histogram below displays the distribution of income among households in the United States in 2001. Suppose a researcher takes a random sample of 60 households and calculates average household income in the sample. Suppose 99 other researchers conduct identical studies, each independently collecting a random sample of 60 households and computing the average household income in that sample.??Which of the following best describes the distribution of the 100 different average household incomes calculated by the researchers?
A. Symmetric with one peak.
B. ?Symmetric with two peaks.
C. ?Skewed left.
D ?Skewed right.
4.When calculating a confidence interval for a mean, which of the following will increase the width of the confidence interval?
A. ?Decreasing the sample size.
B. ?Increasing the sample size.
C. ?Decreasing the sample mean.
D. ?Increasing the sample mean.
5. A manufacturer of microwaves gathers information on microwave sales from a random sample of 50 stores in a large retail chain. In the sample, the mean number of microwaves sold per store last week was 19, with standard deviation 2. ??What is the 95% confidence interval for the mean number of microwaves sold at a retail store in the chain last week?
A ?[18.45, 19.55]
B ?[17.00, 21.00]
C ?[15.00, 23.00]
D ?[18.27, 19.73]
6. In a public opinion poll, 48% of 189 respondents favored an elimination of taxes on dividend income. ??What is the 95% confidence interval for the proportion of people who favor an elimination of taxes on dividend income?
A ?[40.9%, 55.1%]
B ?[47.5%, 48.5%]
C ?[42.0%, 54.0%]
D ?The answer cannot be determined from the information provided.
7.In a public opinion poll, 48% of 189 respondents favor an elimination of taxes on dividend income. ??How many respondents would be needed to calculate a 95% confidence interval (for the proportion of people who favor an elimination of taxes on dividend income) that has a total width no greater than 4% (i.e., the estimate must be within +/- 2% of the true population proportion)?
A ?2,398
B ?600
C ?1,689
D ?The answer cannot be determined from the information provided.
8. In a finance course at a business school, 6 students are randomly selected. Their mean score on the final exam is 75, with standard deviation 8. ??What is the 95% confidence interval for the average class score on the final?
A ?[66.6, 83.4]
B ?[67.6, 82.4]
C ?[68.6, 81.4]
D ?[71.7, 78.3]
9. A company's average accounts receivable per customer is $132.54. After a problem in the automated accounting software is suspected, a random sample of 38 accounts reveals a sample mean of $143.55 and a sample standard deviation of $38.29. ??In a two-sided hypothesis test to see if the average accounts receivable has changed, the best formulation of the null hypothesis is:
A ?The average accounts receivable is $132.54.
B ?The average accounts receivable is $143.55.
C ?The average accounts receivable is no longer $132.54.
D ?None of the above.
10. A company's average accounts receivable per customer is $132.54. After a problem in the automated accounting software is suspected, a random sample of 38 accounts reveals a sample mean of $143.55 and a sample standard deviation of $38.29. ??After running a two-sided hypothesis test of the hypothesis that the average accounts receivable has changed, the best conclusion (using a 95% confidence level) is:
A ?There is not sufficient evidence that the average accounts receivable has changed.
B ?The average accounts receivable is still $132.54.
C ?The average accounts receivable has changed.
D ?The average accounts receivable is at least $143.55.