Locate a confidence interval for the difference of proportions in Exercise 10.16. Show tha...

Locate a confidence interval for the difference of proportions in Exercise 10.16. Show that it reaches the same conclusion as the formal test about the research hypothesis.

Exercise 10.16

A retail computer dealer is trying to decide between two methods for servicing customers' equipment. The first method emphasizes preventive maintenance; the second emphasizes quick response to problems. The dealer serves samples of customers by one of the two methods. After six months, it finds that 171 of 200 customers served by the first method are very satisfied with the service, as compared to 153 of 200 customers served by the second method. Execustat output, based on 1s and 0s for data, follows.

Test the research hypothesis that the population proportions are different. Use α = .05. State your conclusion carefully.