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Unformatted text preview: October 4, 2010 BUAD 310: Applied Business Statistics 1 Outline for Today Two sample inference Two sample confidence intervals Two sample hypothesis testing 2 A Quick Review Hypothesis testing • One sample testing ( used to test the significance of a sample ) z test for a population mean when σ is known or for a population proportion Onesample t test for a population mean when σ is unknown • Two sample testing ( used to compare two samples each from a distinct group ) 3 Two Sample Problems Examples: • Do people with just a Bachelor’s degree earn less than those with a more advanced degree? • A bank wants to know which of the two incentive plans will most increase the use of its credit cards. It offers each incentive to a random sample of customers and compares the amount charged during the following six months. 4 Two Sample Inference The goal of the inference is to compare responses in two groups. • Each group is a distinct category in a population and will be referred to as a distinct population • The responses in each group are independent of those in the other group • Unlike the matched pairs design, there is no matching of the units in the two samples and the two samples may be of different sizes 5 Two Sample Inference Ways to compare two samples: • side by side histograms and boxplots • numerical summaries When both populations are symmetric and especially when they are approximately normal , it is a good idea to compare the mean responses in the two samples 6 Two Sample Inference 7 1. Comparing Two Population Means by Using Independent Samples: Variances Unknown 1. Comparing Two Population Proportions by Using Large Independent Samples Two Sample Inference 8 We want to compare the means either by giving a CI for μ 1  μ 2 or by testing H : μ 1 = μ...
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 '07
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 Statistics, Normal Distribution, Statistical hypothesis testing, p1 − p2

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