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Inferences Based on Two Samples: Confidence Intervals and Tests of Hypothesis Chapter 77.2 a. 1xμ= μ1= 12 111464xnσσ=== .5 b. 2xμ= μ2= 10 222364xnσσ=== .375 c. 12xxμ−= μ1−μ2= 12 −10 = 2 1222221212432646464xxnnσσσ−=+=+=5= .625 d. Since n1≥30 and n2≥30, the sampling distribution of 12xx−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. 2ps= 22112212(1)(1)(251)120(251)100528022525248nsnsnn−+−−+−==+−++= 110 b.2ps= (201)12(101)204082010228−+−=+−= 14.5714 c. 2ps= (61).15(101).22.55610214−+−=+−= .1821 d.2ps= (161)3000(171)250085,0001617231−+−=+−= 2741.9355 e.2psfalls near the variance with the larger sample size. Inferences Based on Two Samples: Confidence Intervals and Tests of Hypothesis 201
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