S4.) There is considerable debate within your firm concerning the effect of advertising on sales. The marketing department believes advertising has a large positive effect; others are not so sure. For instance, the production and technical staffs believe the quality of the product itself largely determines sales. To clarify the debate, you have gathered the following data for the last 24 quarters.

Does advertising affect unit sales? Base your answer on a regression analysis.

Others in the company argue that the last quarters sales best predict this quarters sales. Test this hypothesis via regression analysis. Compare the performances of the regressions in parts (a) and (b).

Some believe the impact of advertising takes time (as long as three months) to affect sales. Perform a regression to test this hypothesis.