[R-meta] Questions about Omnibus tests

[Rafael Rios]

Dear Michael,

Thank you for the help. Indeed, I found a significant p-value in the
QM-test by removing the intercept or using btt(1:3) argumment in the
function rma.mv. However, using such approach, I am testing if each mean
outcome is different than zero. However, I need to test differences among
subgroups by including a value of reference. Such approach needs the
inclusion of intercept:
http://www.metafor-project.org/doku.php/tips:multiple_factors_interactions

I am not sure about the correct approach and what results to report. Can I
really use the QM-test without the intercept to test differences among
subgroups?

Best wishes,

Rafael.
__________________________________________________________

Dr. Rafael Rios Moura
*scientia amabilis*

Behavioral Ecologist, PhD
Postdoctoral Researcher
Universidade Estadual de Campinas (UNICAMP)
Campinas, São Paulo, Brazil

Currículo Lattes: http://lattes.cnpq.br/4264357546465157
ORCID: http://orcid.org/0000-0002-7911-4734
Research Gate: https://www.researchgate.net/profile/Rafael_Rios_Moura2




<http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4244908A8>


Em qui, 25 de out de 2018 às 12:33, Michael Dewey <lists using dewey.myzen.co.uk>
escreveu:

> Dear Rafael
>
> I think the issue is that the test of the intercept tests whether that
> might be zero whereas the test of the moderator tests whether the other
> two coefficients are zero. If you remove the intercept from the model
> you should get a test for the moderator with 3 df (not 2 as at pesent)
> which tests whether all three coefficients are zero which seems to be
> what you are after.
>
> Michael
>
> On 25/10/2018 16:00, Rafael Rios wrote:
> > Dear Wolfgang and All,
> >
> > I am conducting a meta-analysis to evaluate the effects of mate choice
> > on the outcome. My dataset and script follow on attach. I found
> > conflicting results with the omnibus test. The QM-test had a
> > non-significant p-value, while z-test shows a significant p-value for
> > the intercerpt (corresponding to the treatment of female choice). When I
> > undertook pairwise comparisons, I also found differences among
> > treatments consistent with the z-test results. You can also observe
> > these differences in the graph. What exactly is each test (QM and z)
> > evaluating? Why is QM-test reporting a p-value higher than 0.05, even
> > when there is differences in pairwise comparisons? I also found a
> > negative value for I². Is there any problem with the model to report
> > such result? My questions are organized inside the script. Any help will
> > be welcome.
> >
> > Best wishes,
> >
> > Rafael.
> > __________________________________________________________
> >
> > Dr. Rafael Rios Moura
> > /scientia amabilis/
> >
> > Behavioral Ecologist, PhD
> > Postdoctoral Researcher
> > Universidade Estadual de Campinas (UNICAMP)
> > Campinas, São Paulo, Brazil
> >
> > Currículo Lattes: http://lattes.cnpq.br/4264357546465157
> > ORCID: http://orcid.org/0000-0002-7911-4734
> > Research Gate: https://www.researchgate.net/profile/Rafael_Rios_Moura2
> >
> >
> >
> >
> > <http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4244908A8>
> >
> >
> > _______________________________________________
> > R-sig-meta-analysis mailing list
> > R-sig-meta-analysis using r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis
> >
>
> --
> Michael
> http://www.dewey.myzen.co.uk/home.html
>

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