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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 is known or for a population proportion One-sample t test for a population mean when 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 Bachelors 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 1 - 2 or by testing H : 1 =...

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