In Problem 13.4 on page 469, you used efficiency ratio and total risk based capital stored in CommunityBanks to predict ROA at a community bank. Using the results from that problem,
a. Construct a 95% confidence interval estimate of the population slope between ROA and efficiency ratio.
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.