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

[Cesar Terrer Moreno]

I currently have a dataset of 300 observations structures as MeanControl, MeanTreated, SEControl, SETreated, Ncontrol, Ntreated, and I calculate ES and VAR through metafor:escalc.

 

Now, I found a few observations that provide only ES and VAR, which I would like to add to the original dataset.

 

Obviously I could include these new observations ad-hoc to the post-escalc dataset, but journal suggests providing the raw data  with the above fields as MeanControl, MeanTreated, etc so all observations are in the same format. For this reason, I want to back-transform from ES-VAR to MEAN-SE.

 

C

 

De: James Pustejovsky [mailto:jepusto at gmail.com] 
Enviado el: 26 February 2018 15:56
Para: Cesar Terrer Moreno <cesar.terrer at me.com>
CC: r-sig-meta-analysis at r-project.org
Asunto: Re: [R-meta] Calculate individual SDs from ES's SDs

 

No, that's not possible. But why do you need to do this? Couldn't you just use the ES and VAR directly?

 

On Mon, Feb 26, 2018 at 8:53 AM, Cesar Terrer Moreno <cesar.terrer at me.com <mailto:cesar.terrer at me.com> > wrote:

Dear James,

 

I believe you are right, 1.38 is the effect size, and 0.07 the error of the effect size.

 

My question is whether I can compute the standard error of the control and treated groups having the effect size’s SE/SD.

ES = 1.38

VAR = 0.07^2

 

MeanControl = 1

MeanTreated = 1.38

SEControl = ?

SETreated = ?

 

De: James Pustejovsky [mailto:jepusto at gmail.com <mailto:jepusto at gmail.com> ] 
Enviado el: 26 February 2018 15:45
Para: Cesar Terrer Moreno <cesar.terrer at me.com <mailto:cesar.terrer at me.com> >
CC: r-sig-meta-analysis at r-project.org <mailto:r-sig-meta-analysis at r-project.org> 
Asunto: Re: [R-meta] Calculate individual SDs from ES's SDs

 

I would hazard a guess that the +/- 0.07, which is described as "SD", might actually be the standard error of the effect size estimate. So in the example, ES = 1.38 and sampling variance = 0.07^2 = 0.049. Perhaps you can verify this speculation using other information in the source document.

 

James

 

On Wed, Feb 21, 2018 at 6:41 AM, Cesar Terrer Moreno <cesar.terrer at me.com <mailto:cesar.terrer at me.com> > wrote:

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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