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

Viechtbauer, Wolfgang (SP) wo||g@ng@v|echtb@uer @end|ng |rom m@@@tr|chtun|ver@|ty@n|
Tue Nov 2 07:32:03 CET 2021

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'.


>-----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?

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