Continuing Problem 22, suppose that one of the managers of this regional express delivery service company is trying to decide whether to add an interaction term involving the package weight (X1) and the distance shipped (X2) in the previous multiple regression equation.
a. Why would the manager want to add such a term to the regression equation?
b. Estimate the revised equation using the data given in the file P10_22.xlsx.
c. Interpret each of the estimated coefficients in your revised equation. In particular, how do you interpret the coefficient for the interaction term in the revised equation?
d. Does this revised equation fit the data better than the original multiple regression equation? Explain why or why not.