Use the data set GPA1 to answer this question. It was used in Computer Exercise C13 in Chapter 3 to estimate the effect of PC ownership on college GPA.

(i) Run the regression colGPA on PC, hsGPA, and ACT and obtain a 95% confidence interval for bPC. Is the estimated coefficient statistically significant at the 5% level against a two-sided alternative?

(ii) Discuss the statistical significance of the estimates β̂_hsGPA and β̂_hACT in part (i). Is hsGPA or ACT the more important predictor of colGPA?

(iii) Add the two indicators fathcoll and mothcoll to the regression in part (i). Is either individually significant? Are they jointly statistically significant at the 5% level?