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-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of petre...@unina.it Sent: Monday, December 20, 2010 13:26 To: r-help@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 > Facoltà di Medicina e Chirurgia > Università di Napoli Federico II > 081 - 7462233 > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
