[R-meta] Help computing effect size of two-choice test (binary response)

Nathalia Ximenes Gonçalves xg@n@th@||@ @end|ng |rom u@p@br
Wed Nov 3 02:31:40 CET 2021

Dear Wolfgang,

Many thanks for your answer! I don't have any experience with proportions
in meta-analysis. Are they comparable to standardized means and odds ratio?
Is it possible to convert proportions to hedges's g?



Em ter., 2 de nov. de 2021 às 03:32, Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer using maastrichtuniversity.nl> escreveu:

> Dear Nathalia,
> Based on this description, it seems to me that all that you can estimate
> from these studies is the proportion (or some transformation thereof) of
> predators that choose prey with chemical defenses. The choice (prey with
> chemical defense or prey without chemical defense) is an outcome, not a
> 'treament'.
> Best,
> Wolfgang
> >-----Original Message-----
> >From: R-sig-meta-analysis [mailto:
> r-sig-meta-analysis-bounces using r-project.org] On
> >Behalf Of Nathalia Ximenes Gonçalves
> >Sent: Monday, 01 November, 2021 19:18
> >To: r-sig-meta-analysis using r-project.org
> >Subject: [R-meta] Help computing effect size of two-choice test (binary
> response)
> >
> >Hello everyone,
> >
> >I'm conducting a meta-analysis about chemical defenses effectiveness. I'm
> >facing a problem with a set of studies and I was wondering if someone
> could
> >help me. In some studies, the experiment was conducted in a two-choice
> >test, in which the predator had to choose a prey with chemical defense or
> a
> >prey without chemical defense. For instance, if the experiment had 20
> >predators, each one had to choose between two types of prey, let's suppose
> >that 16 predators had choosen prey without chemical defenses and 4
> >predators had choosen prey with chemical defenses. Therefore, I would
> have:
> >'treatment = 4', 'control = 16', and a total sample size of 20. I cannot
> >use any odds ratio, risk ratio, etc metrics, because I don't have a 2x2
> >table, and all the results would be equal to zero if I consider a sample
> >size of 20 for treatment and control separately. Would anyone have any
> >recommendations for calculating the effect size for this type of study?
> >
> >Thanks,
> >
> >Nathalia

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