# [R-meta] Calculate individual SDs from ES's SDs

Viechtbauer Wolfgang (SP) wolfgang.viechtbauer at maastrichtuniversity.nl
Mon Feb 26 15:26:14 CET 2018

```Hit sent on accident before adding:

Best,
Wolfgang

>-----Original Message-----
>From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces at r-
>project.org] On Behalf Of Viechtbauer Wolfgang (SP)
>Sent: Monday, 26 February, 2018 15:25
>To: Cesar Terrer Moreno; r-sig-meta-analysis at r-project.org
>Subject: Re: [R-meta] Calculate individual SDs from ES's SDs
>
>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
```