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Re: st: Meta analysis in single group,


From   David Hoaglin <dchoaglin@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Meta analysis in single group,
Date   Thu, 5 Jan 2012 09:45:48 -0500

What should he do about the possibility of substantial bias when
estimated variances are used in inverse-variance weighting and the
DerSimonian-Laird method?

David Hoaglin

On Thu, Jan 5, 2012 at 7:58 AM, Tiago V. Pereira
<tiago.pereira@mbe.bio.br> wrote:
> Dear Asad,
>
> I solved that problem writing my own code (both fixed-effects 'inverse
> variance' and DerSimonian-Laird methods). They are easy to implement, and
> I think that in your case this is the only way out.
>
> -metan- has an option to perform analyses using the effect and its
> standard error. However, that approach will not be suitable when data is
> continuous, since the normal approximation may not be valid depending on
> the sample size.
>
> To address your question, you need  to estimate the mean difference (pos
> vs pre) for each study. Then, an appropriate variance estimate should be
> computed. To do that, a proper correlation estimate has to be known (or
> estimated from the data).
>
> Once you have the mean effect and its variance, a variance-weighted
> analysis can be performed.
>
> Let me know if you need help.
>
> Tiago

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