Many researchers add one to a frequency before taking the log. If you do that for both observed and expected frequencies, your problem will be solved.
- David Greenberg, Sociology Deparment, New York University
----- Original Message -----
From: "Fenty, J." <[email protected]>
Date: Wednesday, September 1, 2004 7:41 am
Subject: st: Meta-analysis of SMRs
> Dear statlist
>
> I am conducting meta-analyses of SMRs using the -meta- command
> which works fine until you have observed values of zero. I am
> using the formulae
>
> log(SMR) = log(observed/expected)
> se(log(SMR)) = 1/sqrt(observed)
>
> and both are undefined when the observed value=0. Does anyone have
> any suggestions for dealing with this situation other than
> omitting studies with zeroes or combining them with other studies?
> Are there other formulae to calculate se(log(SMR)) which is not
> based solely on the observed value?
>
> Many thanks,
>
> Justin Fenty
>
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