Crash Data The Insurance Institute for Highway Safety conducts experiments in which cars

Chapter 13, Problem 20

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Crash Data The Insurance Institute for Highway Safety conducts experiments in which cars are crashed into a fixed barrier at 40 mph. In the institutes 40-mph offset test, 40% of the total width of each vehicle strikes a barrier on the drivers side. The barriers 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. You are in the market to buy a family car and 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 following data were collected from the institutes 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 The researcher wants to determine if the means for head injury for each class of vehicle are different. (a) State the null and alternative hypotheses. (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. (c) Test the hypothesis that the mean head injury for each vehicle type is the same at the a = 0.01 level of significance. (d) Draw boxplots of the three vehicle types to support the analytic results obtained in part (c).