Unformatted text preview: efore, hypothesis testing conclusions can rely on the interpretation of p‐values. The statistical tables printed in textbook Appendices can have a useful role as a backup check of the test decision. 21 Chapter 11 More Examples of Testing for Equal Population Variances in Two Independent Samples Consider daily stock market closing prices for a company observed in two sample periods. For Johnson & Johnson, a test of equal means in the first and second half of 1999, was developed in the lecture notes for Chapters 9.2 and 11.1. The test method assumed the same variance in the two sample periods. If this variance assumption does not describe the data then the test conclusions may be unreliable. Is the assumption of equal variance in the two sample periods a reasonable assumption ? To answer this question, test the null hypothesis of equal variances in the two samples against a two‐sided alternative. Summary statistics for the closing prices in the two sample periods were reported as: January to June n x = 124 July to December n...
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