Consider the following data:

y x1 x2 x3 x4 y x1 x2 x3 x4 61 37 18 2 13 69 35 21 2 20 37 25 5 4 10 24 23 7 6 9 22 23 12 7 4 68 35 15 3 14 48 12 6 2 15 65 37 19 2 19 66 34 14 3 25 45 30 12 3 12

a. Use standard stepwise regression to produce an estimate of a multiple regression model to predict y.

b. Use forward selection stepwise regression to produce an estimate of a multiple regression model to predict y.

c. Use backward elimination stepwise regression to produce an estimate of a multiple regression model to predict y.

d. Use best subsets regression to produce an estimate of a multiple regression model to predict y.