The monthly incomes for

12

randomly selected people, each with a bachelor's degree in economics, are shown on the right. Complete parts (a) through (c) below.

Assume the population is normally distributed.

4450.24	4596.08	4366.45
4455.31	4151.28	3727.85
4283.15	4527.67	4407.52
3946.78	4023.68	4221.64

A. Find the sample mean.

B. Find the sample standard deviation. (This is what I am having trouble understanding. Please lay out each step clearly)

C. Construct a 95% confidence interval for the population mean.