Fuel Economy. For Exercises 60–67, refer to the table of fuel economy data from Exercises 80–84 in Section 4.2. The predictor variable is , expressed in liters; the response variable is , expressed in miles per gallon (mpg).
61. Calculating and Interpreting .
4.3.61
(a) (b) If we know car's engine size (), then our estimate of the combined mpg will typically differ from the actual mpg by 1.5887 mpg.