No deleted files in chapter 1



6. The following table reports the horsepower, curb weight, and the speed at 1/4 mile for 16 sports and GT cars (1998 Road & Track Sports & GT Cars).

Speed at

Curb Weight 1/4 mile

Sports & GT Car (lb.) Horsepower (mph)

Acura Integra Type R 2577 195 90.7

Acura NSX-T 3066 290 108.0

BMW Z3 2.8 2844 189 93.2

Chevrolet Camaro Z28 3439 305 103.2

Chevrolet Corvette Convertible 3246 345 102.1

Dodge Viper RT/10 3319 450 116.2

Ford Mustang GT 3227 225 91.7

Honda Prelude Type SH 3042 195 89.7

Mercedes-Benz CLK320 3240 215 93.0

Mercedes-Benz SLK230 3025 185 92.3

Mitsubishi 3000GT VR-4 3737 320 99.0

Nissan 240SX SE 2862 155 84.6

Pontiac Firebird Trans Am 3455 305 103.2

Porsche Boxster 2822 201 93.2

Toyota Supra Turbo 3505 320 105.0

Volvo C70 3285 236 97.0

a. Use curb weight as the independent variable and the speed at 1/4 mile as the dependent variable. What is the estimated regression equation?

b. Use curb weight and horsepower as two independent variables and the speed at 1/4 mile as the dependent variable. What is the estimated regression equation?

c. The 1999 Porsche 911 Carrera has been advertised as having a curb weight of 2910 pounds and an engine with 296 horsepower. Use the results in part (b) to predict the speed at 1/4 mile for the Porsche 911.

10. Auto Rental News provided the following data, which show the number of cars in service (1000s), the number of locations, and the rental revenue ($ millions) for 15 car rental companies (The Wall Street Journal Almanac 1998).

Company Cars Locations Revenue

Alamo 130 171 1180

Avis 190 1130 1500

Budget 126 1052 1500

Dollar 63.5 450 560

Enterprise 315.1 2636 2060

FRCS (Ford) 55.25 1784 312.5

Hertz 250 1200 2400

National 135 935 1200

Payless 15 100 47

PROP (Chrysler) 27 1500 160

Rent-A-Wreck 10.9 460 78

Snappy 15.5 259 85

Thrifty 34 480 340

U-Save 13.5 500 95

Value 18 45 150.1

a. Determine the estimated regression equation that can be used to predict the rental revenue given the number of cars in service.

b. Provide an interpretation for the slope of the estimated regression equation developed in part (a).

c. Determine the estimated regression equation that can be used to predict the rental revenue given the number of cars in service and the number of locations.

16. In exercise 6, data were given on curb weight, horsepower, and speed of a sports and GT car at 1/4 mile for 16 cars (1998 Road & Track Sports & GT Cars).

a. Did the estimated regression equation that uses only curb weight to predict the speed at 1/4 mile provide a good fit? Explain.

b. Discuss the benefits of using both the curb weight and the horsepower to predict the speed at 1/4 mile.

18. Refer to exercise 10, where data were reported on the number of cars in service (1000s), the number of locations, and the rental revenue ($ millions) for 15 car rental companies (The Wall Street Journal Almanac 1998).

a. In part (c) of exercise 10, an estimated regression equation was developed relating the rental revenue to the number of cars in service and the number of locations. What are the values of R2 and R2/a?

b. Does the estimated regression equation provide a good fit to the data? Explain.

24. Refer to the data in exercise 6. Use curb weight and horsepower to predict the speed of a sports and GT car at 1/4 mile.

a. Use the F test to determine the overall significance of the relationship. What is your conclusion at the .05 level of significance?

b. Use the t test to determine the significance of each independent variable. What is your conclusion at the .05 level of significance?

26. In exercise 10 an estimated regression equation was developed relating the rental revenue to the number of cars in service and the number of locations.

a. Test for a significant relationship between the dependent variable and the two independent variables. Use α = .05.

b. Is the number of cars in service significant? Use α = .05.

c. Is the number of locations significant? Use α = .05.

30. In exercise 6, data were given on curb weight, horsepower, and speed at Z\v mile for 16 sports and GT cars (1998 Road and Track Sports & GT Cars).

a. Estimate the 1/4-mile speed of a 1999 Porsche 911 Carrera that has a curb weight of 2910 pounds and a horsepower of 296.

b. Provide a 95% confidence interval for the 1/4-mile speed of all sports and GT cars with the characteristics listed in part (a).

c. Provide a 95% prediction interval for the 1999 Porsche 911 Carrera described in part (a).

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