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RE: st: 'Meta' and 'Metareg' Coefficients & CIs Differ


From   "Tiffany Davenport" <tiffany.davenport@yale.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: 'Meta' and 'Metareg' Coefficients & CIs Differ
Date   Mon, 23 Jul 2007 21:45:38 -0400

This syntax works.  Thanks very much.

Tiffany 

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Tom Trikalinos
Sent: Monday, July 23, 2007 8:17 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: 'Meta' and 'Metareg' Coefficients & CIs Differ

I assumed that you have roger harbord's _metareg_ (>=v2.2.6 (?) -
10Dec2004). There was a previous version by stephen sharp...  I do not
recall any specifics for the older command though.

tom

On 7/23/07, Tom Trikalinos <ttrikalin@gmail.com> wrote:
> In the absence of covariates _metareg_ does a random effects 
> meta-analysis, indeed.
> However, with a different method than _meta_ (using the default 
> settings for _metareg_):
>
> _metareg_ uses REML to get the tau^2 estimate (between study variance) 
> _meta_ is using the DerSimonian and Laird method
>
> To get the same results use the following syntax:
>
> metareg beta , wsse(SE) mm z
>
> where mm--> uses the method-of-moments estimate for tau^2, aka the 
> DerSimonian and Laird method z --> uses the z and not the t 
> disrtibution to get the SE and the CIs
>
> tom
>
> On 7/23/07, Tiffany Davenport <tiffany.davenport@yale.edu> wrote:
> > I am using the 'meta' and 'metareg' commands for meta-analysis in 
> > Stata.  As I understand it (and as previously posted) the pooled 
> > random effects estimate obtained by using the 'meta' command should 
> > be the same as the constant obtained in meta-regression analysis 
> > ('metareg') of a model with no covariates.  I am finding that the 
> > values of these estimates as well as their confidence intervals 
> > differ slightly.  I have entered the following
> > syntax:
> >
> > "meta beta SE" - for the meta command and
> >
> > "metareg beta, wsse(SE)" for the meta-regression command
> >
> > 1. Shouldn't the pooled random effects estimate from 'meta' be the 
> > same as the coefficient for the constant from 'metareg,' and 
> > shouldn't the confidence intervals be the same?  If not, I would 
> > appreciate any insight into why the two commands would generate 
> > different estimates with different standard errors.  Are they 
> > weighted differently?  Are adjustments to the syntax of either 
> > command necessary to ensure the intercepts and confidence intervals
match?
> >
> > 2. Is it possible to display more decimal places in the 'meta' output?
> >
> > Thanks very much for any help.
> >
> >
> > *
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> >
>
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