A statistics analyst took a random sample of size 56. The sample mean and standard deviation are 72 and 10, respectively.
a. Determine the 95% confidence interval estimate of the population mean. (3)
b. Change the sample size to = 40, then estimate the 95% confidence interval of the population mean. (3)
c. Describe what happens to the width of the interval when the sample mean decreases. (1)