Statistics for Business: Decision Making and Analysis, 3rd Edition

... United States.

The scatterplot and fitted line show negative association. Heavier cars on average get fewer miles per gallon. The linear pattern attributes about 60% of the variation in mileage to differences in weight (r² = 0.634), and the standard deviation of the residuals is s_e = 2.51 MPG.

Let’s interpret the estimated intercept and slope. The equation of the line is

$$Estimated \text{Combined} \text{MPG}=38.2-4.23 \text{Weight} \left(1,000 \text{lbs}\right)$$

It would be naïve to interpret b₀ as telling us that a “weightless car” would get 38.2 MPG on average; we can instead think of b₀ as the mileage attainable before accounting for moving the mass of a car. The intercept is a reminder that cars burn fuel regardless of their weight to power the air conditioning and electronics. No matter ...