Chapter 7 Even - Inferences Based on Two Samples Confidence...

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Inferences Based on Two Samples: Confidence Intervals and Tests of Hypothesis Chapter 7 7.2 a. 1 x μ = μ 1 = 12 1 1 1 4 64 x n σ σ = = = .5 b. 2 x μ = μ 2 = 10 2 2 2 3 64 x n σ σ = = = .375 c. 1 2 x x μ = μ 1 μ 2 = 12 10 = 2 1 2 2 2 2 2 1 2 1 2 4 3 2 64 64 64 x x n n σ σ σ = + = + = 5 = .625 d. Since n 1 30 and n 2 30, the sampling distribution of 1 2 x x is approximately normal by the Central Limit Theorem. 7.4 Assumptions about the two populations: 1. Both sampled populations have relative frequency distributions that are approximately normal. 2. The population variances are equal. Assumptions about the two samples: The samples are randomly and independently selected from the population. 7.6 a. 2 p s = 2 2 1 1 2 2 1 2 ( 1) ( 1) (25 1)120 (25 1)100 5280 2 25 25 2 48 n s n s n n + + = = + + + = 110 b. 2 p s = (20 1)12 (10 1)20 408 20 10 2 28 + = + = 14.5714 c. 2 p s = (6 1).15 (10 1).2 2.55 6 10 2 14 + = + = .1821 d. 2 p s = (16 1)3000 (17 1)2500 85,000 16 17 2 31 + = + = 2741.9355 e. 2 p s falls near the variance with the larger sample size. Inferences Based on Two Samples: Confidence Intervals and Tests of Hypothesis 201
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