Behaviormetrika
Online ISSN : 1349-6964
Print ISSN : 0385-7417
ISSN-L : 0385-7417
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IS OMEGA SQUARED LESS BIASED? A COMPARISON OF THREE MAJOR EFFECT SIZE INDICES IN ONE-WAY ANOVA
Kensuke Okada
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2013 Volume 40 Issue 2 Pages 129-147

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Abstract

The purpose of this study is to find less biased effect size index in one-way analysis of variance (ANOVA) by performing a thorough Monte Carlo study with 1,000,000 replications per condition. Our results show that contrary to common belief, epsilon squared is the least biased among the threemajorindices, while omega squared produces the least root mean squared errors, for all conditions. Although eta squared results in the least standard deviation, this does not necessarily make it a good estimator because a considerable amount of bias still occurs when the sample size is small.

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© 2013 The Behaviormetric Society
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