Metafor - rma.mv function - variance components

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!
 		 	   		  
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