[R-meta] weight in rmv metafor

[Emerson Del Ponte]

Dear Norman

You may want to check reproducible examples of my previous work on this
exact application context as a starting point.

https://emdelponte.github.io/paper-white-mold-meta-analysis/

https://emdelponte.github.io/paper-FHB-yield-loss/code_meta_analysis.html

Emerson




On Thu, 11 Jun 2020 at 10:06 Norman DAURELLE <
norman.daurelle using agroparistech.fr> wrote:

>
> Thank you.
> I am not sure I understand exactly what you mean by " i f the working
> model is only an approximation and doesn't cover all dependencies ".
> Could you please explain it ?
>
> For now I used the rma() function to synthesize the available literature
> existing on the blackleg - oil seed rape disease-yield relationship, using
> slopes as effect-sizes.
> the models that gave me the slopes I used in the meta-analysis are all Y =
> a + bX, simple linear regressions with Y being the yield and X being the
> diseqse severity.
> So my slopes, b, are all negative, and I have obtained a "summary" effect
> size through the rma() function.
>
> But I indeed have two studies that for now contribute to most of the
> effect-sizes that are included in my meta-analysis.
>
> So why exactly is it necessary to use the rma.mv() function ?
> What exactly does the "multivariate" qualificative refer to ?
>
> Thank you,
> Norman.
>
>
> De: "Wolfgang Viechtbauer" <wolfgang.viechtbauer using maastrichtuniversity.nl>
> À: "Norman DAURELLE" <norman.daurelle using agroparistech.fr>,
> "r-sig-meta-analysis" <r-sig-meta-analysis using r-project.org>
> Envoyé: Jeudi 11 Juin 2020 22:34:55
> Objet: RE: [R-meta] weight in rmv metafor
>
> Dear Norman,
>
> If you only used rma(), then this is not correct. rma.mv() with an
> appropriately specified model (plus clubSandwich::coef_test() if the
> working model is only an approximation and doesn't cover all dependencies)
> would be more appropriate.
>
> Best,
> Wolfgang
>
> >-----Original Message-----
> >From: Norman DAURELLE [mailto:norman.daurelle using agroparistech.fr]
> >Sent: Thursday, 11 June, 2020 14:13
> >To: r-sig-meta-analysis
> >Cc: Viechtbauer, Wolfgang (SP)
> >Subject: Re: [R-meta] weight in rmv metafor
> >
> >Hi all,
> >
> >I read this discussion and one question came to my mind : I also had some
> >studies that contributed multiple effect sizes in the meta-analysis that
> I
> >recently ran thanks to Dr Viechtbauer's advice.
> >For now I only used the rma function, but should I have used rma.mv
> because
> >of these stuides that had multiple effect sizes ?
> >
> >Thank you !
> >
> >Norman
> >
> >________________________________________
> >De: "James Pustejovsky" <jepusto using gmail.com>
> >À: "Wolfgang Viechtbauer" <wolfgang.viechtbauer using maastrichtuniversity.nl>
> >Cc: "r-sig-meta-analysis" <r-sig-meta-analysis using r-project.org>, "Huang
> Wu"
> ><huang.wu using wmich.edu>
> >Envoyé: Mercredi 10 Juin 2020 05:08:09
> >Objet: Re: [R-meta] weight in rmv metafor
> >
> >Hi Huang,
> >
> >I've written up some notes that add a bit of further intuition to the
> >discussion that Wolfgang provided. The main case that I focus on is a
> model
> >that is just a meta-analysis (i.e., no predictors) and that includes
> random
> >effects to capture both between-study and within-study heterogeneity. I
> >also say a little bit about meta-regression models with only study-level
> >predictors.
> >
> >https://www.jepusto.com/weighting-in-multivariate-meta-analysis/
> >
> >Best,
> >James
> >
> >On Sun, Jun 7, 2020 at 4:11 PM Viechtbauer, Wolfgang (SP) <
> >wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:
> >
> >> Of course the weights "impact the estimated fixed effects". But whether
> >> studies with multiple effect sizes tend to receive more weight depends
> on
> >> various factors, including the variances of the random effects and the
> >> sampling error (co)variances.
> >>
> >> A more detailed discussion around the way weighting works in rma.mv
> >> models can be found here:
> >>
> >> http://www.metafor-project.org/doku.php/tips:weights_in_rma.mv_models
> >>
> >> Note that weights(res, type="rowsum") currently only works in the
> 'devel'
> >> version of metafor, so follow
> >> https://wviechtb.github.io/metafor/#installation if you want to
> reproduce
> >> this part as well.
> >>
> >> I hope this clarifies things.
> >>
> >> Best,
> >> Wolfgang
>
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>
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-- 
*Emerson M. Del Ponte*
Universidade Federal de Viçosa, Brazil
Chair of the Graduate Studies <http://www.dfp.ufv.br/graduate/> in Plant
Pathology
EIC for Tropical Plant Pathology <http://sbfitopatologia.org.br/tpp/>
Co-Founder of Open Plant Pathology <https://www.openplantpathology.org/>
My websites: Twitter <https://twitter.com/edelponte> | GitHub
<https://github.com/emdelponte> | Google Scholar
<https://scholar.google.com.br/citations?user=a1rPnI0AAAAJ> | ResearchGate
<https://www.researchgate.net/profile/Emerson_Del_Ponte>
Tel +55 31 36124830

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