In Problem 13.5 on page 470, the percentage of alcohol and chlorides were used to predict the quality of red wines (stored in VinhoVerde). Develop a regression model that includes the percentage of alcohol, the chlorides, and the interaction of the percentage of alcohol and the chlorides to predict wine quality.
a. At the 0.05 level of significance, is there evidence that the interaction term makes a significant contribution to the model?
b. Which regression model is more appropriate, the one used in this problem or the one used in Problem 13.5? Explain.