Chapter B.6, Problem 20AYU

Crash Data The Insurance Institute for Highway Safety conducts experiments in which cars are crashed into a fixed barrier at 40 mph. The barrier’s deformable face is made of aluminum honeycomb, which makes the forces in the test similar to those involved in a frontal offset crash between two vehicles of the same weight, each going just less than 40 mph. Suppose you want to know if the mean head injury resulting from this offset crash is the same for large family cars, passenger vans, and midsize utility vehicles. The researcher wants to determine if the means for head injury for each class of vehicle are different. The following data were collected from the institute’s study.

Large Family Cars	Head Injury (hic)
Hyundai XG300	264
Ford Taurus	134
Buick LeSabre	409
Chevrolet Impala	530
Chrysler 300	149
Pontiac Grand Prix	627
Toyota Avalon	166
Passenger Vans	Head Injury (hic)
Toyota Sienna	148
Honda Odyssey	238
Ford Freestar	340
Mazda MPV	693
Chevrolet Uplander	550
Nissan Quest	470
Kia Sedona	322
Midsize Utility Vehicles	Head Injury (hic)
Honda Pilot	225
Toyota 4Runner	216
Mitsubishi Endeavor	186
Nissan Murano	307
Ford Explorer	353
Kia Sorento	552
Chevy Trailblazer	397

Source: Insurance Institute for Highway Safety

1. (a) State the null and alternative hypotheses.
2. (b) Verify that the requirements to use the one-way ANOVA procedure are satisfied. Normal probability plots indicate that the sample data come from normal populations.
3. (c) Test the hypothesis that the mean head injury for each vehicle type is the same at the α = 0.01 level of significance.
4. (d) Draw boxplots of the three vehicle types to support the analytic results obtained in part (c).