In a multiple regression with 40 observations, the following sample regression equation is obtained: = 12.8 + 2.6x1 1 .2x2 with se =

In a multiple regression with 40 observations, the following sample regression equation is obtained: ŷ = 12.8 + 2.6x1 −

1 .2x2 with se = 5.84. Also, when x1 equals 15 and x2 equals 6, se(ŷ0) = 2.20.

a. Construct a 95% confidence interval for E(y ) if x1 equals 15 and x2 equals 6.

b. Construct a 95% prediction interval for y if x1 equals 15 and x2 equals 6.

c. Which interval is wider? Explain.