[R-meta] Calculate individual SDs from ES's SDs
Viechtbauer Wolfgang (SP)
wolfgang.viechtbauer at maastrichtuniversity.nl
Mon Feb 26 15:24:31 CET 2018
As far as I can tell, you can't. But what is that 0.07 SD supposed to be a standard deviation of anyway? And n=3 for each group or was there only a single group that was measured under both conditions? (which is a different case than the usual ratio of means effect size, which assumes independence between groups).
>-----Original Message-----
>From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces at r-
>project.org] On Behalf Of Cesar Terrer Moreno
>Sent: Wednesday, 21 February, 2018 13:41
>To: r-sig-meta-analysis at r-project.org
>Subject: [R-meta] Calculate individual SDs from ES's SDs
>
>Dear all,
>
>I have a series of effects sizes, expressed as e.g.:
>
>1.38 ± 0.07 (MEANexp/MEANcontrol, SD, n=3)
>
>I have to express these experiments as MEANexp, SDexp, MEANcontrol,
>SDcontrol in order to put all data in a correct formar that can be read
>by escalc in metafor.
>
>I guess I can assume MEANexp = 1.38 and MEANcontrol = 1, but how can I
>compute SDs so that escalc computes the effect size’s variance properly?
>
>Thanks
>César
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