More traffic Here’s a plot of Studentized residuals against Congested% for the model of Exercise 13. The plot is colored according to City Size, and regression lines are fit for each size

a) The model of Exercise 13 includes indicators for City Size. Considering this display, have these indicator variables accomplished what is needed for the regression model? Explain.
We constructed additional indicators as the product of Small with Arterial mph and the product of Very Large with Arterial mph. Here’s the resulting model:
Response variable is: Congestion per auto commuter ($)
R-squared = 64.9, R-squared (adjusted) = 63.1, s = 149.9 with 101 - 6 = 95 degrees of freedom

b) What does the predictor Sml*C,V (Small by Congestion%)
do in this model? Interpret the coefficient.

c) Does this appear to be a good regression model?
Would you consider removing any predictors? Why or why not?

Studentized Residuals 2.50 1.25 0.00 -1.25 20 40 60 Congested% of VMT 80 80