[R-meta] metafor: standardized mean change using raw score standardization
@pyr|don@@|@||@ @end|ng |rom tum@de
Wed Aug 7 14:15:23 CEST 2019
Thank you very much for your clarification!
It was not so clear to me.
Von: Wolfgang Viechtbauer <wolfgang.viechtbauer using maastrichtuniversity.nl>
Gesendet: Wednesday, August 7, 2019 2:05 PM
An: Spyridon Siafis <spyridon.siafis using tum.de>
Cc: r-sig-meta-analysis using r-project.org
Betreff: Re: [R-meta] metafor: standardized mean change using raw score standardization
Indeed, 'sd2i' isn't needed, since escalc() computes yi=(m1i-m2i)/sd1i for measure="SMCR". If you have the mean change (and not the pre- and post-test means), then you can set m1i to the mean change and m2i to 0.
But you will need to specify 'ri' and cannot simply assume it to be 0. The value of 'ri' won't change the size of 'yi', but it will influence the size of the sampling variance ('vi').
> Hello to all,
> I would like to calculate standardized mean change with raw score standardization ("SMCR") using the escalc().
> Therefore: sd1i=pre-test standard deviation, m1i= mean change score or post-test mean and m2i=0 or pre-test mean, respectively.
> As far as I understood, the arguments sd2i and ri are not needed for the calculations, but they are required in escalc.
> Could I use sd2i=0 and ri=0? Do they influence the calculations?
> Thank you very much in advance!
> All the best,
> Spyros Siafis
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