7. Now suppose that I add a second predictor variable to the regression model: hours per week spent working for money. And suppose that the correlation between hours spent working and hours spent studying is −.50. The correlation between the two predictor variables (number of close friends and hours spent working for money) is −.30.

a. What effect do you think the addition of this second predictor variable will have on the overall amount of variance explained (R2) in the dependent variable? Why?

b. What effect do you think the addition of this second predictor variable will have on the strength of the regression coefficient for the first predictor variable, compared to when only the first predictor variable was in the regression model? Why?

For answers to these work problems, and for additional work problems, please refer to the website that accompanies this book.