In problem 12.4 on page 423, you used the percentage of alcohol to predict wine quality. Perform a residual analysis for these data (stored in Vinho Vercla). Evaluate whether the assumptions of regression have been seriously violated.
In problem 12.4
The production of wine is a multibillion dollar worldwide industry. In an attempt to develop a model of wine quality as judged by wine experts, data was collected from red wine variants of Portuguese “ Vinho Verde” wine. (Data ­extracted from P. Cortez, Cerdeira, A., Almeida, F., Matos, T., and Reis, J., “ Modeling Wine Preferences by Data Mining from Physiochemical Properties,” Decision Support Systems, 47, 2009, pp. 547– 553 and bit. ly/ 9xKlEa.) A sample of 50 wines is stored in VinhoVerde . Develop a simple linear regression model to predict wine quality, measured on a scale from 0 (very bad) to 10 (excellent), based on alcohol content (%).