QMS 202 Study Guide - Mann–Whitney U Test, Pooled Variance

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12. 1: comparing the means of 2 independent populations. Z test for the difference between 2 means test stat - determine diff b/ pop means based on diff b/ sample means. Pooled-variance t-test for the diff between 2 means variances unknown only info sample means and sample variances assume sample randomly and independently selected f/ pop. Pooled variance t-test pop variances equal ( 1 n1 and n2 30 = at least. H0: 1 = 2 or 1 - 2 = 0. H1: 1 2 or 1 - 2 0. 2 = best estim under assumption 2 pop variance are. 2-tail test: reject h0: tstat > critical val t-test tstat < critical val t-test. One tail test: reject h0: tstat < lower tail critical val t-test or tstat > upper tail critical val t-test + - t /2. 2 = variance of pop n = size of pop.