16. Problem 23 in Chapter 10 described a study demonstrating that elderly people who own dogs are less likely to pay visits to their doctors than are those who do not own pets. The data are presented again here.

Number of Doctor Visits in Past Year Control Group Dog Owners 10 7 8 4 7 9 9 3 13 7 7

6 12 Use these data to estimate how much difference there is in the number of doctor visits for people with dogs compared to those without.

a. Make a point estimate of the mean difference between the two populations.

b. Make a 90% confidence interval estimate of the population mean difference.