The weight of a car is an important determinant of its fuel efficiency.

The weight of a car is an important determinant of its fuel efficiency. Below is a scatterplot of the relationship between vehicle weight in tons (WT_TONS) against fuel efficiency (Miles per Gallon), based upon an analysis of 398 different models of cars. Also included is output from the bivariate regression in which miles per gallon is predicted by WT_TONS:

a)   Write the regression equation that describes the relationship between vehicle weight and fuel efficiency.

b)   Interpret the coefficient on "WT_TONS", in your equation above, in plain English.

c)   Draw the regression line onto the figure. (It may be helpful to start by putting in two points that you know are on the line).