In Problem 14.5 on page 583, you used horsepower and weight to predict mileage (stored in Auto2010). Use the results from that problem.
a. Construct a 95% confidence interval estimate of the population slope between mileage and horsepower.
b. At the 0.05 level of significance, determine whether each independent variable makes a significant contribution to the regression model. On the basis of these results, indicate the independent variables to include in this model.