Consider the vehicle data from Consumer Reports in Figure XXXXXXXXXXWeight is in tons, mileage in miles per gallon, and drive ratio is also indicated. A regression model was fitted relating weight x...

Consider the vehicle data from Consumer Reports in Figure 11.30. Weight is in tons, mileage in miles per gallon, and drive ratio is also indicated. A regression model was fitted relating weight x to mileage y. A partial SAS printout in Figure 11.30 shows some of the results of that regression analysis, and Figure 11.31 gives a plot of the residuals and weight for each vehicle.

Figure 11.30: SAS printout, showing partial analysis

Figure 11.31:SASprintout, showing residual plot

(a) From the analysis and the residual plot, does it appear that an improved model might be found by using a transformation? Explain.

(b) Fit the model by replacing weight with log weight. Comment on the results.

(c) Fit a model by replacing mpg with gallons per 100 miles traveled, as mileage is often reported in other countries. Which of the three models is preferable? Explain.