After analyzing whether the number of ads is related to the number of customers, the manager in Exercise 16.99 decided to determine whether the advertising made any difference. As a result, he reorganized the experiment. Each week he advertised several times per week, but in only one of the advertising media. He again recorded the weekly number of customers, the number of ads, and the media of that week’s advertisement (1 = Newspaper, 2 = Radio, 3 = Television).

a. Create indicator variables to describe the advertising medium.

b. Conduct a regression analysis. Test to determine whether the model is valid.

c. Does the advertising medium make a difference? Explain.