[R] Metafor: Differences between two categories of a moderator

[Viechtbauer Wolfgang (STAT)]

Well, that's a good question. It actually applies to many different contexts (not just meta-analysis). Think of the ANOVA F-test and post-hoc/planned contrasts. It's essentially the same situation. And if you would ask 10 different statisticians about this, you may get 11 different answers.

My suggestion would be this: If you have no particular hypotheses in mind and are just screening for group differences, then adjust. If you have a priori hypotheses, then test them without adjustment (and in that case, you may even ignore the omnibus test).

Best,

--
Wolfgang Viechtbauer
Department of Psychiatry and Neuropsychology
School for Mental Health and Neuroscience
Maastricht University, P.O. Box 616
6200 MD Maastricht, The Netherlands
Tel: +31 (43) 368-5248
Fax: +31 (43) 368-8689
Web: http://www.wvbauer.com
________________________________________
From: r-help-bounces at r-project.org [r-help-bounces at r-project.org] On Behalf Of Holger Steinmetz [Holger.steinmetz at web.de]
Sent: Wednesday, June 01, 2011 10:10 AM
To: r-help at r-project.org
Subject: Re: [R] Metafor: Differences between two categories of a moderator

Hi Wolfgang

that's good news. One further small follow-up question: When I conduct
multiple comparisons via the relevel-command: should I adjust the p-value?

Thanks in advance,
Holger

--
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