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


From   "Tom Trikalinos" <ttrikalin@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: 'Meta' and 'Metareg' Coefficients & CIs Differ
Date   Mon, 23 Jul 2007 20:12:11 -0400

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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