QUESTION 8

If the sample mean is 102, the population standard deviation is 14, and the sample size is 63, construct a 99% confidence interval of the population mean.

A. [97.46, 106.54]

B. [95.16, 105.34]

C. [98.54, 105.46]

D. [99.10, 104.90]

9. National Science Foundation is estimating the average total salary of full professors in the math department. Data were randomly collected from 20 professors and the 95% confidence interval for the mean was calculated to be ($95,201, $108,030). What additional assumption is necessary for this confidence interval to be valid?

A. None. The Central Limit Theorem applies.

B. The sample standard deviation is less than the degrees of freedom.

C. The population of total salaries of full professors in math is approximately normally distributed.

D. The distribution of the sample means is approximately normal.

QUESTION 11

The data below contains the amount that a sample of ten customer spent for lunch ($) at a fast-food restaurant.

4.52; 5.44; 5.72; 6.25; 6.46; 7.28; 7.52; 8.46; 8.62; 9.23

Construct a 99% confidence interval for the population mean amount spent for lunch at a fast-food restaurant assuming a normal distribution.

A. [5.85, 8.05]

B. [6.06, 7.84]

C. [5.38, 8.52]

D. [6.27, 7.62]

QUESTION 16

A local eat-in pizza restaurant wants to investigate the possibility of starting to deliver pizzas. The owner of the store has determined that home delivery will be successful only if the average time spent on a delivery does not exceed 40 minutes. The owner has randomly selected 17 customers and delivered pizzas to their homes in order to test whether the mean delivery time actually exceeds 40 minutes. Suppose the p-value for the test was found to be .0293. State the incorrect conclusion.

A. With significance level 0.03, we fail to reject the null.

B. With significance level 0.03, we fail to reject the null.

C. With significance level 0.05, we fail to reject the null.

D. With significance level 0.01, we reject the null.

QUESTION 22

Which statement is not true about confidence interval?

A. Given the same confidence level, a wider interval is less precise

B. In practice, we want the confidence interval to be relatively narrow given a fixed confidence leve.

C. The width of a confidence interval is determined by the sample size.

D. The width of a confidence interval is determined by the sample mean

QUESTION 23

In testing for the differences between the means of 2 independent populations where the variances in each population are unknown but assumed equal, what are the degrees of freedom? we know their sample sizes are 10 and 12, respectively.

A. 20

B. 21

C. 22

D. 23