[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 16:17:30 CET 2021
Dear Michael,
I agree with you. My interest in converting the proportions is because the
majority of my data are means or odds, so I wanted to include these
proportions in the same meta-analytic model.
Nathalia
Em qua., 3 de nov. de 2021 às 06:04, Michael Dewey <lists using dewey.myzen.co.uk>
escreveu:
> Dear Nathalia
>
> The other two effect sizes you mention are comparative ones (SMD and OR)
> so proportions will not be comparable to them.
>
> Why would you want to convert them to another metric? Proportions have a
> straightforward intuitive interpretation, everyone knows what a half
> means, but who knows what g=0.5 means without some thought? If at the
> end of your analysis you can say that predators prefer untreated prey
> 0.75 of the time then does that not answer your scientific question?
>
> Michael
>
> On 03/11/2021 01:31, Nathalia Ximenes Gonçalves wrote:
> > 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?
> >
> > Thanks,
> >
> > Nathalia
> >
> > 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
> >>
> >
> > [[alternative HTML version deleted]]
> >
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> >
>
> --
> Michael
> http://www.dewey.myzen.co.uk/home.html
>
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