18. R2 in Predicting Baseball Pitcher Performance. Refer to exercise 10, where Major League Baseball (MLB) pitching statistics were reported for a random sample of 20 pitchers from the American League for one full season.

a. In part

(c) of exercise 10, an estimated regression equation was developed relating the average number of runs given up per inning pitched given the average number of strikeouts per inning pitched and the average number of home runs per inning pitched. What are the values of R2 and R2a ?

b. Does the estimated regression equation provide a good fit to the data? Explain.

c. Suppose the earned run average (ERA) is used as the dependent variable in part (c)
instead of the average number of runs given up per inning pitched. Does the estimated regression equation that uses the ERA provide a good fit to the data? Explain.