According to the document All About Diabetes, found on the Web site of the American Diabetes Association, ". . .diabetes is a disease in which the body does not produce or properly use insulin, a hormone that is needed to convert sugar, starches, and other food into energy needed for daily life." A random sample of 15 diabetics yielded the data on ages, in years, presented on the WeissStats CD. Use the technology of your choice to do the following.
a. Find a 95% confidence interval for the mean age, μ, of all people with diabetes. Assume that σ = 21.2 years.
b. Obtain a normal probability plot, boxplot, histogram, and stem-and-leaf diagram of the data.
c. Remove the outliers (if any) from the data, and then repeat part (a).
d. Comment on the advisability of using the z-interval procedure on these data.