[R-meta] aggregating effect sizes

[Viechtbauer, Wolfgang (SP)]

Dear Filippo,

If you are asking about what is described in Box 24.1, then the answer is yes, if you use struct='CS' (which is the default) and 'weighted=FALSE' -- the default in aggregate() is to compute a weighted average, but Borenstein et al. only give the equations for computing an unweighted average and its sampling variance (but since the sampling variances of the two estimates that are being aggregated in the book example are the same, whether one uses weighted=TRUE or FALSE makes no difference). You can also find the corresponding code here:

https://wviechtb.github.io/meta_analysis_books/borenstein2009.html#24)_Multiple_Outcomes__Time-Points

Best,
Wolfgang

>-----Original Message-----
>From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org] On
>Behalf Of Filippo Gambarota
>Sent: Monday, 10 January, 2022 12:31
>To: R meta
>Subject: [R-meta] aggregating effect sizes
>
>Hi,
>In order to be sure which function to use I would like to ask if the
>aggregation method of multiple effect sizes with dependent sampling
>error suggested by Borenstein et al. (2009) is the same as what
>performed by the aggregate() function in metafor specifying a single
>correlation.
>In my case I have calculated pre-post effect size using Morris (2008)
>and then I have to combine multiple effect sizes calculated on the
>same pool of subjects.
>Thank you!
>
>--
>Filippo Gambarota
>PhD Student - University of Padova
>Department of Developmental and Social Psychology
>Website: filippogambarota
>Research Group: Colab   Psicostat