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J Appl Psychol. 2005 Jan;90(1):94-107.

Effect size and power in assessing moderating effects of categorical variables using multiple regression: a 30-year review.

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The Business School, University of Colorado at Denver, Denver, CO 80217, USA.


The authors conducted a 30-year review (1969-1998) of the size of moderating effects of categorical variables as assessed using multiple regression. The median observed effect size (f(2)) is only .002, but 72% of the moderator tests reviewed had power of .80 or greater to detect a targeted effect conventionally defined as small. Results suggest the need to minimize the influence of artifacts that produce a downward bias in the observed effect size and put into question the use of conventional definitions of moderating effect sizes. As long as an effect has a meaningful impact, the authors advise researchers to conduct a power analysis and plan future research designs on the basis of smaller and more realistic targeted effect sizes.

[Indexed for MEDLINE]

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