46. The U.S. Department of Energy’s Fuel Economy Guide provides fuel efficiency data for cars and trucks. A portion of the data for 35 standard pickup trucks produced by Chevrolet and General Motors follows (http://www.fueleconomy.gov, March 21, 2003). The column labeled Drive identifies whether the vehicle has two-wheel drive (2WD) or four-wheel drive (4WD). The column labeled Displacement shows the engine’s displacement in liters, the column labeled Cylinders specifies the number of cylinders the engine has, and the column labeled Transmission shows whether the truck has an automatic transmission or a manual transmission. The column labeled City MPG shows the fuel efficiency rating for the truck for city driving in terms of miles per gallon (mpg)

a. Develop an estimated regression equation that can be used to predict the fuel efficiency for city driving given the engine’s displacement. Test for significance using α .05.

b. Consider the addition of the dummy variable Drive4, where the value of Drive4 is 0 if the truck has two-wheel drive and 1 if the truck has four-wheel drive. Develop the estimated regression equation that can be used to predict the fuel efficiency for city driving given the engine’s displacement and the dummy variable Drive4.

c. Use α .05 to determine whether the dummy variable added in part

(b) is significant.

d. Consider the addition of the dummy variable EightCyl, where the value of EightCyl is 0 if the truck’s engine has six cylinders and 1 if the truck’s engine has eight cylinders. Develop the estimated regression equation that can be used to predict the fuel efficiency for city driving given the engine’s displacement and the dummy variables Drive4 and EightCyl.

e. For the estimated regression equation developed in part (d), test for overall significance and individual significance using α .05

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City Truck Name Drive Displacement Cylinders Transmission MPG 1 C1500 Silverado 2WD 4.3 6 Auto 15 2 C1500 Silverado 2WD 4.3 6 Manual 3 C1500 Silverado 2WD 4.8 4. C1500 Silverado 2WD 4.8 5 C1500 Silverado 2WD 5.3 33 K1500 Sierra 4WD 5.3 34 Sonoma 4WD 4.3 35 Sonoma 4WD 4.3 00 00 00 00 6 8 Auto 15 8 Manual 16 Auto 11 8 Auto 15 6 Auto 17 Manual 15 SESSI 575 15