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Determining the Presence of Moderator Variables

When conducting a meta-analysis, look for moderating variables. These are third factors that may influence the relationship of interest. Hunter et al. (1982) present a Chi-Square test for systematic variation, which is useful in determining whether there is a moderator variable present.

Where K is the number of studies in the analysis. If the Chi-square is not statistically significant, then no moderator variable is present. Statistically this is a very powerful test, given a large enough N, it will reject the null hypothesis even if there is only trivial variation among studies. Alternatively Hunter et al (1982) give a rule of thumb, in which S2r and S2er are compared. If the error variance accounts for less than 75% of the uncorrected variance, then a moderator variable may be present.

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