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From | "Tiago V. Pereira" <tiago.pereira@mbe.bio.br> |
To | statalist@hsphsun2.harvard.edu |
Subject | st: RE: Question regarding Trim and Fill method using 'metatrim' |
Date | Sun, 5 Sep 2010 15:26:16 -0300 (BRT) |
Dear Chan, If I got the big picture correctly, your results seem to be OK: the command is correct and the results are intuitive. Firstly, as the test for small-study effects indicates that there is no substantial bias, it is reasonable to expect some agreement between it and the 'trim and fill' approach. In other words, there is no reason to expect the trim and fill to adjust for publication bias if it in fact doesn't exist. If you have raw data (i.e. 2x2 tables), try to investigate small study effect using the Harbord's test as well (metabias a b c d, harbord) Secondly, I would be very concerned to use the trim and fill approach in results showing strong evidence for statistical heterogeneity. This seems to be the case in your data set of 13 studies: Q= 41.214 (12 df) and estimated tau^ = 0.023. To understand the problem, see: http://www.ncbi.nlm.nih.gov/pubmed/12820277 http://www.ncbi.nlm.nih.gov/pubmed/17476644 Thirdly, visual inspection of the funnel plot is highly subjective with 13 studies only. Indeed, the asymmetry in the funnel plot that you see may be either entirely subjective or a result of the statistical heterogeneity across study results. hope this helps. 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/