Do heavier cars use more gasoline? To answer this question, a researcher randomly selected 15 cars. He collected their weight (in hundreds of pounds) and the mileage (MPG) for each car. From a scatterplot made with the data, a linear model seemed appropriate. The following output was obtained from SAS:

R-Square Root MSE 0.438 6.78 Parameter Estimate Standard t Value Pr > It| Error Intercept 40.439 6.275 6.445 0.0000 WEIGHT -0.521 0.164 -3.182 0.0072