Metafor package
Dear Mario, 1) Whether to use 1/2* or not is arbitary. It's just a multiplicative constant. 2) vi <- 1/(4*ni + 2) If one leave off the 1/2* part, then it would be vi <- 1/(ni + 1/2). 3) Yes, but it takes a bit more work. Fortunately, the same issue was raised not very long ago, so the following post should essentially answer your question: https://stat.ethz.ch/pipermail/r-help/2010-December/263286.html Best, -- Wolfgang Viechtbauer Department of Psychiatry and Neuropsychology School for Mental Health and Neuroscience Maastricht University, P.O. Box 616 6200 MD Maastricht, The Netherlands Tel: +31 (43) 368-5248 Fax: +31 (43) 368-8689 Web: http://www.wvbauer.com ----Original Message---- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of petretta at unina.it Sent: Monday, December 20, 2010 13:26 To: r-help at r-project.org Subject: [R] Metafor package
I have some question about metafor package. I'm interest to perform a random effect meta-analysis of proportion (single group summary of prevalence of disease in a population as reported by different study) It ask: 1. "PFT": The Freeman-Tukey double arcsine transformed proportion is reported to be equal to 1/2*(asin(sqrt(xi/(ni+1))) + asin(sqrt((xi+1)/(ni+1)))). Hovewer, i also found the same formula but without 1/2*. 2. how "vi", the corresponding (estimated) sampling variance is calculated? (i.e. the formula used to estimate "vi") 3. it is possible to return a forest plot with the backtransformed value of proportion, confidenc interval and weight and not with the transformed value after performing rma.uni? Many thanks Mario Petretta Dipartimento di Medicina Clinica Scienze Cardiovascolari e Immunologiche Facolt? di Medicina e Chirurgia Universit? di Napoli Federico II 081 - 7462233
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