Fuel Economy. Refer to the following table of fuel economy data for a sample of 10 vehicles for Exercises 80–84. The predictor variable is , expressed in liters; the response variable is , expressed in miles per gallon (mpg).

Vehicle
Mini Cooper 1.6 31
Ford Focus 2.0 28
Toyota Camry 2.5 26
Honda Accord 2.4 26
Subaru Forester 2.5 23
Toyota Highlander 2.7 22
Ford Taurus 3.5 20
Chevrolet Equinox 3.0 19
Dodge Nitro 4.0 17
Cadillac limousine 4.6 14

Question 4.181

enginempg

83. Regression. Answer the following:

  1. Calculate the slope of the regression equation. Does the sign of agree with your prediction from Exercise 81(c)?
  2. Calculate the intercept .
  3. Interpret the values you calculated in parts (a) and (b), so that a nonstatistician would understand them.

4.2.83

(a) ; yes (b) = 38.41 (c) The slope of means that the combined mpg will decrease by 5.49 mpg for each 1-liter increase in engine size. The intercept of is the predicted combined mpg for an engine size of 0 liters.