11-2 Contingency Tables 603 Study,” by Wells et al., BMJ USA, Vol. 4). Test the claim that injuries are independent of helmet color. Should motorcycle drivers choose helmets with a particular color? If so, which color appears best? Color of Helmet Black White Yellow, Orange Red Blue Controls (not injured) 491 377 31 170 55 Cases (injured or killed) 213 112 8 70 26 17. Survey Refusals A study of people who refused to answer survey questions provided the randomly selected sample data shown in the table below (based on data from “I Hear You Knocking But You Can’t Come In,” by Fitzgerald and Fuller, Sociological Methods and Research, Vol. 11, No. 1). At the 0.01 significance level, test the claim that the cooperation of the subject (response or refusal) is independent of the age category. Does any particular age group appear to be particularly uncooperative? Age 18–21 22–29 30–39 40–49 50–59 60 and over Responded 73 255 245 136 138 202 Refused 11 20 33 16 27 49 18. Genetics and Handedness In a study of left-handedness as a possible inherited trait, the data in the table below were obtained (based on data from “Why Are Some People LeftHanded? An Evolutionary Perspective,” by Laurens and Faurie, Philosophical Transactions, Vol. 364). Use a 0.01 significance level to test the claim that handedness of offspring is independent of parental handedness. What do the results suggest about the inheritability of handedness? Handedness of Parents (Father, Mother) Handedness of Offspring Left Right Right>Right 5360 50,928 Right>Left 767 2736 Left>Right 741 3667 Left>Left 94 289 19. Car License Plates California, Connecticut, and New York are states with laws requiring that cars have license plates on the front and rear. The author randomly selected cars in those states and the results are given in the accompanying table. Use a 0.05 significance level to test the claim of independence between the state and whether a car has front and rear license plates. Does it appear that the license plate laws are followed at the same rates in the three states? California Connecticut New York Car with Rear Plate Only 35 45 9 Car with Front and Rear Plates 528 289 541 20. Is the Home Field Advantage Independent of the Sport? Winning team data were collected for teams in different sports, with the results given in the table below (based on data from “Predicting Professional Sports Game Outcomes from Intermediate Game Scores,” by Copper, DeNeve, and Mosteller, Chance, Vol. 5, No. 3–4). Use a 0.10 significance level to test the claim that home>visitor wins are independent of the sport. Given that among the four sports included here, baseball is the only sport in which the home team can modify field dimensions to favor its own players, does it appear that baseball teams are effective in using this advantage? Basketball Baseball Hockey Football Home Team Wins 127 53 50 57 Visiting Team Wins 71 47 43 42
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