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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 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/