a. A random sample of 100 observations was randomly drawn from a population with a standard deviation of 5. The sample mean was calculated as . Estimate the population mean with 99% confidence.

b. Repeat part

(a) with .

c. Repeat part

(a) with .

d. Describe what happens to the width of the confidence interval estimate when the sample mean decreases.

x = 100 x = 200 x = 400 x = 500 x = 200 x = 100 s = 20 n = 25 x

x = 500 x = 500 s = 12 n = 50 Exercises 10.17 to 10.20 are based on the optional subsection

“Estimating the Population Mean Using the Sample Median.”

All exercises assume that the population is normal.