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Sample size determinations for Welch's test in one‐way heteroscedastic ANOVA
Author(s) -
Jan ShowLi,
Shieh Gwowen
Publication year - 2014
Publication title -
british journal of mathematical and statistical psychology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.157
H-Index - 51
eISSN - 2044-8317
pISSN - 0007-1102
DOI - 10.1111/bmsp.12006
Subject(s) - heteroscedasticity , sample size determination , context (archaeology) , variance (accounting) , statistics , sample (material) , analysis of variance , mathematics , homoscedasticity , type i and type ii errors , range (aeronautics) , one way analysis of variance , econometrics , power (physics) , computer science , engineering , paleontology , chemistry , accounting , chromatography , business , biology , aerospace engineering , physics , quantum mechanics
For one‐way fixed effects ANOVA , it is well known that the conventional F test of the equality of means is not robust to unequal variances, and numerous methods have been proposed for dealing with heteroscedasticity. On the basis of extensive empirical evidence of Type I error control and power performance, Welch's procedure is frequently recommended as the major alternative to the ANOVA F test under variance heterogeneity. To enhance its practical usefulness, this paper considers an important aspect of Welch's method in determining the sample size necessary to achieve a given power. Simulation studies are conducted to compare two approximate power functions of Welch's test for their accuracy in sample size calculations over a wide variety of model configurations with heteroscedastic structures. The numerical investigations show that Levy's (1978a) approach is clearly more accurate than the formula of Luh and Guo (2011) for the range of model specifications considered here. Accordingly, computer programs are provided to implement the technique recommended by Levy for power calculation and sample size determination within the context of the one‐way heteroscedastic ANOVA model.