[R-meta] meta-analysis with 2 within-subject variables

[Viechtbauer, Wolfgang (NP)]

Dear Tom,

I don't have any worked examples for this. However, before rma.mv(), the first step is the calculation of the effect sizes, their sampling variances, and covariances if there are multiple effect sizes for a given group. I assume you want to compute the pre-post change for each condition, so that would be two effects for a group. Is the response variable dichotomous or continuous? And if it is continuous, is the scale the same across studies (so one can stick to mean differences) or does it differ across studies (so one has to consider effect size measures that are comparable across different scales)?

Best,
Wolfgang

> -----Original Message-----
> From: R-sig-meta-analysis <r-sig-meta-analysis-bounces using r-project.org> On Behalf
> Of zeffiro neurometrika.org via R-sig-meta-analysis
> Sent: Tuesday, December 3, 2024 17:27
> To: r-sig-meta-analysis using r-project.org
> Cc: zeffiro neurometrika.org <zeffiro using neurometrika.org>
> Subject: [R-meta] meta-analysis with 2 within-subject variables
>
>  I have a question about how to set up the metafor code to perform a meta-
> analysis using an experimental design that is fairly common in cross-over
> treatment studies.
>
>  We have continuous outcome measures (mean and sd) from studies in which each
> participant was measured 4 times: 1) in both drug and placebo conditions and 2)
> both before and after exposure - in a cross-over design. So,
> each study is a 2x2 factorial design with 2 repeated measures.
>
> Although it looks to me as if rma.mv is the appropriate program for this
> analysis, I am having difficulty determining the syntax showing how to set
> things up to properly handle the within subject correlation and was hoping that
> someone could point me to a worked example to use as a guide. I have not found
> anything addressing meta-analysis modeling of multiple repeated measures in a
> single group.
>
> We are starting out with only 5 studies in the initial meta-analysis.
>
> Thanks in advance for any guidance you can provide.
>
> Regards,
> Tom