8 Review Exercises 456 CHAPTER 8 Hypothesis Testing with Two Samples Section 8.1 In Exercises 1–4, classify the two samples as independent or dependent and justify your answer. 1. Sample 1: The heights of 37 children Sample 2: The heights of the same 37 children after 1 year 2. Sample 1: The weights of 45 oranges Sample 2: The weights of 40 grapefruits 3. Sample 1: The retail prices of 20 motorcycles Sample 2: The retail prices of 20 minivans 4. Sample 1: The fuel efficiencies of 12 cars Sample 2: The fuel efficiencies of the same 12 cars using an alternative fuel In Exercises 5–8, test the claim about the difference between two population means m1 and m2 at the level of significance a. Assume the samples are random and independent, and the populations are normally distributed. 5. Claim: m1 Ú m2; a = 0.05 Population statistics: s1 = 0.30 and s2 = 0.23 Sample statistics: x1 = 1.28, n1 = 96 and x2 = 1.34, n2 = 85 6. Claim: m1 = m2; a = 0.01 Population statistics: s1 = 52 and s2 = 68 Sample statistics: x1 = 5595, n1 = 156 and x2 = 5575, n2 = 216 7. Claim: m1 6 m2; a = 0.10 Population statistics: s1 = 0.11 and s2 = 0.10 Sample statistics: x1 = 0.28, n1 = 41 and x2 = 0.33, n2 = 34 8. Claim: m1 ≠ m2; a = 0.05 Population statistics: s1 = 14 and s2 = 15 Sample statistics: x1 = 87, n1 = 410 and x2 = 85, n2 = 340 In Exercises 9 and 10, (a) identify the claim and state H0 and Ha, (b) find the critical value(s) and identify the rejection region(s), (c) find the standardized test statistic z, (d) decide whether to reject or fail to reject the null hypothesis, and (e) interpret the decision in the context of the original claim. Assume the samples are random and independent, and the populations are normally distributed. 9. A researcher claims that the mean sodium content of sandwiches at Restaurant A is less than the mean sodium content of sandwiches at Restaurant B. The mean sodium content of 22 randomly selected sandwiches at Restaurant A is 670 milligrams. Assume the population standard deviation is 20 milligrams. The mean sodium content of 28 randomly selected sandwiches at Restaurant B is 690 milligrams. Assume the population standard deviation is 30 milligrams. At a = 0.05, is there enough evidence to support the claim? 10. A career counselor claims that the mean annual salaries of entry level paralegals in Dayton, Ohio, and Coventry, Rhode Island, are the same. The mean annual salary of 40 randomly selected entry level paralegals in Dayton is $58,180. Assume the population standard deviation is $10,990. The mean annual salary of 35 randomly selected entry level paralegals in Coventry is $61,120. Assume the population standard deviation is $11,850. At a = 0.10, is there enough evidence to reject the counselor’s claim? (Adapted from Salary.com)
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