An experiment involves selecting a random sample of 256 middle managers for study. One item of interest is annual income. The sample mean is computed to be 35,420, and the sample standard deviation is 2,050.

a) What is the estimated mean income of all middle managers (the population)?

b) Give a 95 percent confidence interval (rounded to the nearest 10) for your estimate of the mean income. Do you have to make any assumptions?

c) Interpret the meaning of the confidence interval.