A plot of Studentized residuals against predicted values for the regression model found in now looks like this. It has been colored according to Type of pizza and separate regression lines fitted for each type:
a) Comment on this diagnostic plot. What does it say about how the regression model deals with cheese and pepperoni pizzas? Based on this plot, we constructed yet another variable consisting of the indicator Type multiplied by Calories: b) Interpret the coefficient of Type*Cals in this regression model. c) Would you prefer this regression model to the model of? Explain.
