Suppose that daily changes in the Dow-Jones Average of Industrial Stocks are normally distributed and that the change on any given day is independent of the change on any other day. A random sample of 81 daily changes is obtained, with sample mean .20 and sample variance (s2) 1.50. Find a 90 per¬

cent confidence interval for p, the population mean. Suppose that a second random sample is obtained, with a sample size of 25, a sample mean of .15, and a sample variance of 1.20. Using the information from both samples, find a 90 percent confidence interval for p. How reasonable are the assump¬

tions in this problem?