Section 7.3 #23 and 37 23. A microwave oven repairer says that the mean repair cost for damaged microwave ovens is less than $100.You work for the repairer and want to test this claim. You find that a random sample of five microwave ovens has a mean repair cost of $75 and a standard deviation of $12.50. At α = 0.01 do you have enough evidence to support the repairer’s claim? 37. In Exercises 37 and 38, decide whether you should use a normal sampling distribution or a t-sampling distribution to perform the hypothesis test. Justify your decision. Then use the distribution to test the claim. Write a short paragraph about the results of the test and what you can conclude about the claim. A car company says that the mean gas mileage for its luxury sedan is at least 21 miles per gallon (mpg).You believe the claim is incorrect and find that a random sample of 5 cars has a mean gas mileage of 19 mpg and a standard deviation of 4 mpg. Assume the gas mileage of all of the company’s luxury sedans is normally distributed. At α = 0.05, test the company’s claim. Section 7.4 #10 and 12 In Exercises 9 “�14, (a) write the claim mathematically and identify H_0 and H_a, (b) find the critical values and identify the rejection regions, (c) find the standardized test statistic, and (d) decide whether to reject or fail to reject the null hypothesis. Then interpret the decision in the context of the original claim. 10. A medical researcher estimates that no more than 55% of U.S. adults eat breakfast every day. In a random sample of 250 U.S. adults, 56.4% say that they eat breakfast every day. At α = 0.01, is there enough evidence to reject the researcher’s claim? 12. An environmentalist claims that more than 50% of British consumers want supermarkets to stop selling genetically modified foods. You want to test this claim. You find that in a random sample of 100 British consumers, 53% say that they want supermarkets to stop selling genetically modified foods. At α = 0.10, can you support the environmentalist’s claim? Section 7.5 #17 and 26 In Exercises 17″�26, (a) write the claim mathematically and identify H_0 and H_a (b) find the critical value(s) and identify the rejection region(s), (c) use the x²-test to find the standardized test statistic, and (d) decide whether to reject or fail to reject the null hypothesis. Then interpret the decision in the context of the original claim. Assume the populations are normally distributed. 17. A large appliance company estimates that the variance of the life of its appliances is 3. You work for a consumer advocacy group and are asked to test this claim. You find that a random sample of the lives of 27 of the company’s appliances has a variance of 2.8. At α = 0.05, do you have enough evidence to reject the company’s claim? 26. An employment information service says that the standard deviation of the annual salaries for public relations managers is at least $14,500. The annual salaries for 18 randomly chosen public relations managers are listed. At α = 0.10, can you reject the claim?
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