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Re: st: how to pool prevalences


From   Nicola Orsini <Nicola.Orsini@imm.ki.se>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: how to pool prevalences
Date   Sun, 06 Nov 2005 16:58:02 +0100

Hi,
what about this

// suppose you have 4 studies

clear
input study cases total
1 20 1000
2 40 5000
3 30 1500
4 25 3300
end

gen p = .
gen se = .

// get proportions and std errors

forv i =1(1)4 {
     cii total[`i'] cases[`i']
     qui replace p = r(mean) in `i'
     qui replace se = r(se) in  `i'
}

// get the inverse variance-weighted proportion
// use the official Stata -vwls- command

gen cons =1
vwls p cons, sd(se)

// use the user written -metan- command

// fixed-effects meta-analysis
metan p se, nograph fixed

// random-effects meta-analysis
metan p se, nograph random

Nicola

b. water wrote:
> Thanks Svend,
> 
> Not quite sure that is legit. Could be biased by study(ies) from 
> higher/lower risk populations, which would skew their rates. I think 
> there is no Stata user solution. At the moment, I am thinking of using 
> 'the inverse variance-weighted' method to pool. Vaguely I think there 
> was a criticism about this method but would have to do for now.
> 
> Other advice, help and opinion are still welcome.
> 
> Thanks once again.
> 
> Regards,
> bw
> 
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