Re: st: Meta-analysis and corr2data

[Richard Williams <Richard.A.Williams.5@nd.edu>]

At 01:48 AM 3/9/2004 -0800, n p wrote:

> statistics etc.). The question is if it is right to
> use the corr2data command to create three (or more)
> independent samples for A, B and C arms with given
> mean, SE and N to obtain via regression two betas and
> two SEs (B vs. A and C vs. A). I know that I could use
> only two arms for each meta-analysis ( B vs. A, C vs.
> A and so on) but I think that this would induce some
> multiple comparison error so I decided that I have to
> calculate all possible betas of each study ( B vs. A,
> C vs. A and so on) simultaneously.
I think you  could.  You would run corr2data multiple times to create each 
of the fake data sets, adding an indicator to each data set to indicate 
which group it was (e.g. gen group = 1, gen group = 2, etc.)  Then, combine 
all the files together.

If in doubt as to whether what you are doing with corr2data is 
legit:  Generate alternative data sets, using a different seed.  Results 
should be exactly identical, down to several decimal places.  If not, what 
you are doing is probably illegitimate.  For example, computing logs of 
variables would not be legitimate.

Basically, the idea behind corr2data is that you can use it when the means, 
correlations and standard deviations are sufficient to do all the required 
calculations.  If anything more than that is needed, corr2data can't handle 
it.  In some programs, like SPSS, you could enter means, correlations and 
SDs directly.  In Stata, you achieve the same thing via the creation of 
fake data with the desired means, etc.  But, you have to remember that the 
data are fake!  And what you can do is limited.

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Richard Williams, Notre Dame Dept of Sociology
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