13.2 Observations are taken on sales of a certain mountain bike in 30 sporting goods stores. The regression model was Y = total sales (thousands of dollars), X1 = display floor space (square meters), X2 = competitors’ advertising expenditures (thousands of dollars), X3 = advertised price (dollars per unit). (a) Write the fitted regression equation. (b) Interpret each coefficient. (c) Would the intercept seem to have meaning in this regression? (d) Make a prediction for Sales when FloorSpace = 80, CompetingAds = 100, and Price = 1,200.

Predictor          Coefficient
Intercept             1225
FloorSpace             11.52
CompetingAds       −6.935
Price                      −0.1496

13.4 Refer to the ANOVA table for this regression. (a) State the degrees of freedom for the F test for overall significance. (b) Use Appendix F to look up the critical value of F for α = .05. (c) Calculate the F statistic. Is the regression significant overall? (d) Calculate R2 and R2adj, showing your formulas clearly.

Source                d.f.          SS                MS
Regression          3          1,196,410       398,803
Error                   26          379,332          14,590
Total                   29       1,575,742

13.6 Observations are taken on sales of a certain mountain bike in 30 sporting goods stores. Theregression model was Y = total sales (thousands of dollars), X1 = display floor space (square meters), X2 = competitors’ advertising expenditures (thousands of dollars), X3 = advertised price (dollars per unit), X4 = rebate rate (percent of retail price). (a) Calculate the t statistic for each coefficient to test for β = 0. (b) Look up the critical value of Student’s t in Appendix for a two-tailed test at α = .01. Which coefficients differ significantly from zero? (c) Use Excel to find the p-value for each coefficient.

Predictor          Coefficient                SE
Intercept                   1225.4                   397.3
FloorSpace                   11.522                   1.330
CompetingAds             −6.935                   3.905
Price                            −0.14955             0.08927

13.2 Observations are taken on sales of a certain mountain bike in...