Chapter 14, Problem 19PS

In Problem 14.5 on page 542, you used the percentage of alcohol and chlorides to predict wine quality (stored in VinhoVerde).

a. Plot the residuals versus ${\hat{Y}}_i$

b. Plot the residuals versus $X_{1i.}$

c. Plot the residuals versus $X_{2i.}$

d. In the residuals plots created in (a) through (c), is there any evidence of a violation of the regression assumptions? Explain.

e. Should you compute the Durbin-Watson Statistic for these data? Explain.