[R-meta] moderator and adjusted effects

[Valeria Ivaniushina]

Dear experts,

In my sample of articles for meta-analysis there are three categories, or
three conditions, that may influence the effect of interest.

I am more interested in estimating different effects from these conditions
than in explaining heterogeneity in effect sizes.
1) I can do a meta-analysis for each of these conditions separately and get
three different mean effect sizes.
2) Or I can do a meta-analysis of the whole sample, then include a
condition as a moderator and calculate adjusted effects as described here :
http://www.metafor-project.org/doku.php/tips:computing_adjusted_effects

Which option is better?

Additional question:  when I include a categorical moderator, is it the
same as including a dummy variable in a regression?
How can I specify that the variable is categorical with 3 levels?

Best,
Valeria

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