[R] Metafor - rma.mv function - variance components
Michael Dewey
lists at dewey.myzen.co.uk
Tue Apr 21 14:43:44 CEST 2015
Dear Carlijn
You might shed some light on what is going on by using
profile.rma.mv
Michael
On 21/04/2015 09:42, Carlijn Wibbelink wrote:
> Thank you for your reaction, it worked.
> However, I'm wondering if this is the right way to test whether there is
> significant variation on one of the two levels. The results of the anova
> tests do not correspond to the results of the Z-test in metaSEM. (In
> metaSEM only one of the variances is significant, but when I use the
> anova test in metafor, both variances are significant). But maybe I made
> a mistake. This is my syntax:
> model2 <- rma.mv(y, v, random = list(~ 1 | y, ~ 1 | ID), data=dat)
> model3 <- rma.mv(y, v, random = list(~ 1 | y, ~ 1 | ID), sigma2=c(NA,0),
> data=dat)
> model4 <- rma.mv(y, v, random = list(~ 1 | y, ~ 1 | ID), sigma2=c(0,NA),
> data=dat)
> anova(model2,model3)
> anova(model2,model4)
>
> Is it possible to receive the standard errors of the variances in
> metafor (and do a Z-test)?
>
>
> > To: wibbeltjec at hotmail.com; r-help at r-project.org
> > Subject: Re: [R] Metafor - rma.mv function - variance components
> > From: Lists at dewey.myzen.co.uk
> > Date: Mon, 20 Apr 2015 20:24:48 +0000
> >
> > Carlijn Wibbelink <wibbeltjec at hotmail.com> wrote :
> >
> > Dear Carlijn
> > I think that if you set sigma2 to a vector of length 2 it will be
> possible.
> >
> > > Hi all,
> > >
> > > I have a question about metafor and the rma.mv function. I have
> fitted a
> > > multivariate model (effect sizes are nested within studies) and
> I've found two
> > > variances:
> > >
> > > Variance Components:
> > > estim sqrt nlvls fixed factor
> > > sigma^2.1 0.0257 0.1602 72 no y
> > > sigma^2.2 0.0694 0.2635 10 no ID
> > >
> > > I want to test whether there is significant variantion between the
> effect sizes
> > > within studies (sigma^2.1: 0.0257) and/or between studies
> (sigma^2.2: 0.0694).
> > > In metaSEM you can fix for example the variance within studies
> (sigma^2.1) to
> > > zero to test whether there is a significant difference in fit
> between the models
> > > (and if so, then there is significant heterogeneity between the
> effect sizes
> > > within studies). I was wondering if this is also possible in
> metafor. If I fix
> > > sigma2 to zero, then both variances are fixed to zero. However, I
> want to fix
> > > only one variance to zero.
> > > I hope that someone can help me. Thank you in advance!
> > >
> > > [[alternative HTML version deleted]]
> > >
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> >
> >
> >
> >
--
Michael
http://www.dewey.myzen.co.uk/home.html
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