The director of marketing at Vanguard Corporation believes that sales of the company's Bright Side laundry detergent (S) are related to Vanguard's

 0.3250            2.63                0.0128

R                    −0.284                  0.164              −1.73              0.0927

a. Interpret the sign of coefficients a, b, and c.

b. Does Vanguard's advertising expenditure have a statistically significant effect on the

sales of Bright Side detergent? Explain, using the appropriate p-value.

c. Does advertising by its three largest rivals affect sales of Bright Side detergent in a

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statistically significant way? Explain, using the appropriate p-value.

d. What fraction of the total variation in sales of Bright Side remains unexplained? What

can the marketing director do to increase the explanatory power of the sales equation?

What other explanatory variables might be added to this equation?

e. What is the expected level of sales each week when Vanguard spends $30,000 per week

and the combined advertising expenditures for the three rivals are $200,000 per week?