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Mann-Whitney u test when variances are unequal

Mann-Whitney u test when variances are unequal

Animal Behaviour 61(6): 47-9

The type 1 error rate of the Mann-Whitney U test is shown to inflate under unequal variance. This test is one of the most widely used statistical tests in studies of behavior. Although it, like many other nonparametric tests based on rank, assumes equal variances in 2 populations, authors usually use the test without examining whether the variances are equal. Alternative procedures for use when the variances are different are suggested.

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Accession: 009903182

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DOI: 10.1006/anbe.2001.1691

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