Metafor package: Including multiple (categorical) predictors
The test of moderator coefficients (QM) is chi-square distributed.You can use the change in this value when you add a predictor to the model as a chi-square test, with df equal to the change in df. Jeremy
On 2 August 2012 05:54, Bexkens, Anika <A.Bexkens at uva.nl> wrote:
Dear Metafor users,
I'd like to test a model with 2 continuous and 2 categorical moderators in a meta regression. One categorical parameter has 2 levels and the other has 4 levels. If I understand correctly, when I include all moderators in the model, Metafor returns main effects of the continuous parameters and contrasts of each level of categorical moderators with the intercept (which includes the reference level of the categorical parameters).
This makes it possible to see whether different levels of the categorical moderator are differentially related to effect size. I include multiple moderators and would like to report for each variable whether it is significantly moderating effect size. Is it possible to obtain an overall main effect of each categorical variable, instead of the contrast effects? Or can I only obtain this by including one categorical moderator at a time and reporting the omnibus moderator test?
Many thanks,
Anika
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