Suppose that the variables y, x1, and x2 are related by the regression model...

Suppose that the variables y, x₁, and x₂ are related by the regression model

a. Construct a graph (similar to that of Figure 14.5) showing the relationship between mean y and x₂ for fixed values 10, 20, and 30 of x₁.

b. Construct a graph depicting the relationship between mean y and x₁ for fixed values 50, 55, and 60 of x₂.

c. What aspect of the graphs in Parts (a) and (b) can be attributed to the lack of an interaction between x₁ and x₂?

d. Suppose the interaction term .03x₃ where x₃ = x₁x₂ is added to the regression model equation. Using this new model, construct the graphs described in Parts (a) and (b). How do they differ from those obtained in Parts (a) and (b)?