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Asked Jan 13, 2020

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Are Seat Belts Effective? A simple random sample of front-seat occupants involved in car crashes is obtained. Among 2823 occupants not wearing seat belts, 31 were killed. Among 7765 occupants wearing seat belts, 16 were killed (based on data from “Who Wants Airbags?” by Meyer and Finney, Chance, Vol. 18, No. 2). We want to use a 0.05 significance level to test the claim that seat belts are effective in reducing fatalities.

a. Test the claim using a hypothesis test.

b. Test the claim by constructing an appropriate confidence interval.

c. What does the result suggest about the effectiveness of seat belts?

Step 1

Solution: We are given:

Among 2823 occupants not wearing seat belts, 31 were killed. Among 7765 occupants wearing seat belts, 16 were killed

Step 2

Let p1 be the proportion of occupants not wearing the seat belts who got killed and p2 be the proportion of occupants wearing the seat belts who got killed. Therefore, we have:

Step 3

a. Test the claim using a hypothesis test.

Answer: The nul...

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