15. In exercise 5, the owner of Showtime Movie Theaters, Inc., used multiple regression analy- sis to predict gross revenue (y) as a function of television advertising (x,) and newspaper advertising (x,). The estimated regression equation was = 83.2 + 2.29x + 1.30.x2 The computer solution provided SST = 25.5 and SSR = 23.435.

a. Compute and interpret R and R.

b. When television advertising was the only independent variable, R2 = .653 and R = .595. Do you prefer the multiple regression results? Explain.