For the multiple regression equation obtained in Exercise 16.11:
a. At the 0.05 level, is the overall regression equation significant?
b. Use the 0.05 level in concluding whether each partial regression coefficient differs significantly from zero.
c. Interpret the results of the preceding tests in the context of the variables described in that exercise.
d. Construct a 95% confidence interval for each partial regression coefficient in the population regression equation.