Ages of Diabetics. According to the document All About Diabetes, found on the website 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 site. 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 stemand-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.