[R-meta] fixed-effect multivariate model interpretation

[Filippo Gambarota]

Thank you Wolfgang!
So my related question is how this residual heterogeneity is estimated in
order to compute the Q statistic? Because if the model is still estimating
and testing the presence of heterogeneity, from a multivariate model I
would have expected one residual heterogeneity term for each outcome (the
same as I have one tau per outcome if I fit the random-effect version).

On Mon, 3 Jan 2022 at 16:50, Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:

> Hi Filippo,
>
> You can *assume* that there is no residual heterogeneity, but there may
> be. That is what the test of residual heterogeneity is testing here
> (whether your assumption is correct or not).
>
> Best,
> Wolfgang
>
> >-----Original Message-----
> >From: R-sig-meta-analysis [mailto:
> r-sig-meta-analysis-bounces using r-project.org] On
> >Behalf Of Filippo Gambarota
> >Sent: Monday, 03 January, 2022 16:42
> >To: R meta
> >Subject: [R-meta] fixed-effect multivariate model interpretation
> >
> >Hello!
> >I'm fitting for the first time a multivariate fixed-effect model using
> >metafor. The code is:
> >
> >```
> >rma.mv(yi, V, mods = ~ 0 + outcome, data = data, test = "t")
> >```
> >Where V is the block variance-covariance matrix created with vcalc()
> >that represents the covariance between different outcome levels within
> >each study. The outcome is a factor that represents different effect
> >sizes measured on the same participants within a study.
> >The model as expected did not estimate tau for each outcome and test
> >all coefficients (each outcome mean with this parametrization) against
> >0 (both the omnibus test and each beta). My question is about the
> >*residual heterogeneity* parameter and the associated Q test. Under
> >this model, I should have assumed that there is no heterogeneity
> >within each outcome level so I'm not sure how to interpret the
> >residual heterogeneity in this case.
> >Thank you!
> >Filippo
> >
> >--
> >Filippo Gambarota
> >PhD Student - University of Padova
> >Department of Developmental and Social Psychology
> >Website: filippogambarota.netlify.app
> >Research Group: Colab   Psicostat
>


-- 
*Filippo Gambarota*
PhD Student - University of Padova
Department of Developmental and Social Psychology
Website: filippogambarota.netlify.app
Research Group: Colab <http://colab.psy.unipd.it/>   Psicostat
<https://psicostat.dpss.psy.unipd.it/>

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