Use the 4-8Cyl data set to calculate the two regression equations shown in Figures 3.10 and 3.11.
a. Does the Radj2 value increase when the interaction term is added? Based on the change in Radj2, should the interaction term be included in the model?
b. For both models, calculate the estimated price of a four- cylinder car when Mileage = 10,000.
c. Assuming Mileage = 10,000, for both models explain how increasing from four to eight cylinders will impact the estimated price.
d. Conduct an extra sum of squares test to determine if the MileCyl interaction term is important to the model.