21. How large of a sample is needed to estimate the population mean for the money a person spends on Christmas presents within $2 and be 95% confident? The standard deviation of the population is $7.50.

A. 54

B. 54

C. 55

D. 56

22. It is said that blood type O is the most common type. I want to know if gender has any bearing on the relative number of people with blood type O. What test should I perform?

A. Two sample proportion z-test

B. One sample chi-square test

C. One sample proportion z-test

D. Two sample F-test

23. Which of the following is TRUE regarding the sampling distribution of the means?

A. The mean of the sample means will differ from the population mean.

B. The standard deviation of the sample means will be the one-half of the value of the population standard deviation.

C. The computed mean of the sample means will be greater by a factor of 1.5 than the population mean.

D. The standard deviation of the sample is equal to the population standard deviation divided by the square root of the sample size.

24. What test can be used to test the difference between two sample means when the population variances are known?

A. Z-test

B. Chi-Square Test

C. t-Test

D. F-Test