A80 ODD ANSWERS Uses and Abuses for Chapter 8 (page 454) 1. Answers will vary. 2. Blind: The patients do not know which group (medicine or placebo) they belong to. Double-blind: Both the researcher and patient do not know which group (medicine or placebo) that the patient belongs to. Review Exercises for Chapter 8 (page 456) 1. Dependent because the same children were sampled. 3. Independent because different vehicles were sampled. 5. Fail to reject H0. There is not enough evidence at the 5% level of significance to reject the claim. 7. Reject H0. There is enough evidence at the 10% level of significance to support the claim. 9. (a) The claim is “the mean sodium content of chicken sandwiches at Restaurant A is less than the mean sodium content of chicken sandwiches at Restaurant B.” H0: m1 Ú m2; Ha: m1 6 m2 (claim) (b) z0 = -1.645; Rejection region: z 6 -1.645 (c) -2.82 (d) Reject H0. (e) There is enough evidence at the 5% level of significance to support the researcher’s claim that the mean sodium content of chicken sandwiches at Restaurant A is less than the mean sodium content of chicken sandwiches at Restaurant B. 11. Reject H0. There is enough evidence at the 5% level of significance to reject the claim. 13. Fail to reject H0. There is not enough evidence at the 10% level of significance to reject the claim. 15. Reject H0. There is enough evidence at the 1% level of significance to support the claim. 17. (a) The claim is “the new method of teaching mathematics produces higher mathematics test scores than the old method does.” H0: m1 … m2; Ha: m1 7 m2 (claim) (b) t0 = 1.667; Rejection region: t 7 1.667 (c) 2.313 (d) Reject H0. (e) There is enough evidence at the 5% level of significance to support the claim that the new method of teaching mathematics produces higher mathematics test scores than the old method does. 19. Reject H0. There is enough evidence at the 1% level of significance to reject the claim. 21. Reject H0. There is enough evidence at the 10% level of significance to reject the claim. 23. (a) The claim is “the numbers of runs scored in a season by NCAA Division 1 baseball teams changed from 2019 to 2021.” H0: md = 0; Ha: md ≠ 0 (claim) (b) -t0 = -2.262, t0 = 2.262 Rejection region: z 6 -2.262, z 7 2.262 (c) d = 38.1; sd ≈ 66.10 (d) 1.823 (e) Fail to reject H0. (f) There is not enough evidence at the 5% level of significance to support the claim that the numbers of runs scored in a season by NCAA Division 1 baseball teams changed from 2019 to 2021. 25. Can use normal sampling distribution. Fail to reject H0. There is not enough evidence at the 5% level of significance to reject the claim. 27. Can use normal sampling distribution. Reject H0. There is enough evidence at the 10% level of significance to support the claim. 29. (a) The claim is “the proportion of subjects who had at least 24 weeks of accrued remission is the same for the two groups.” H0: p1 = p2 (claim); Ha: p1 ≠ p2 (b) -z0 = -1.96, z0 = 1.96 Rejection regions: z 6 -1.96, z 7 1.96 (c) 4.03 (d) Reject H0. (e) There is enough evidence at the 5% level of significance to reject the medical research team’s claim that the proportion of subjects who had at least 24 weeks of accrued remission is the same for the two groups. Quiz for Chapter 8 (page 460) 1. (a) The claim is “the mean score on the reading assessment test for male high school students is less than the mean score for female high school students” H0: m1 Ú m2; Ha: m1 6 m2 (claim) (b) Left-tailed because Ha contains 6; z-test because s1 and s2 are known, the samples are random samples, samples are independent, and n1 Ú 30 and n2 Ú 30. (c) z0 = -1.645; Rejection region: z 6 -1.645 (d) -1.616 (e) Fail to reject H0. (f) There is not enough evidence at the 5% level of significance to support the claim that the mean score on the reading assessment test for male high school students is less than the mean score for female high school students. 2. (a) The claim is “the mean scores on a music assessment test for eighth grade students in public and private schools are equal.” H0: m1 = m2 (claim); Ha: m1 ≠m2 (b) Two-tailed because Ha contains ≠; t-test because s1 and s2 are unknown, the samples are random samples, the samples are independent, and the populations are normally distributed. (c) -t0 = -1.706, t0 = 1.706 Rejection region: t 6 -1.706, t 7 1.706 (d) -0.814 (e) Fail to reject H0. (f) There is not enough evidence at the 10% level of significance to reject the claim that the mean scores on a music assessment test for eighth grade students in public and private schools are equal. 3. (a) The claim is “the seminar helps adults increase their credit scores.” H0: md Ú 0; Ha: md 6 0 (claim)
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