The computer output for the multiple regression analysis for Exercise 13.3 provides this information:

a. Which, if any, of the independent variables x1, x2, and x3 contribute information for the prediction of y?
b. Give the least-squares prediction equation.
c. On the same sheet of graph paper, graph y versus x1 when x2 = 1 and x3 = 0 and when x2 = 1 and x3 = .5. What relationship do the two lines have to each other?
d. What is the practical interpretation of the parameter β1?

bi = 1.29 SE(b) = .42 by = .41 SE(b) = .17 b2 = 2.72 SE(b) = .65