Refer to Exercise 13.1.
a. Graph the relationship between E(y) and x2 when x1 = 0. Repeat for x1 = 1 and for x1 = 2. b. What relationship do the lines in part a have to one another?
c. Suppose, in a practical situation, you want to model the relationship between E(y) and two predictor variables x1 and x2. What is the implication of using the first-order model E(y) = b0 = b1x1 = b2x2?