[R] Metafor package

[petretta at unina.it]

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