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Re: st: Strate-confidence interval method

From   "Svend Juul" <SJ@SOCI.AU.DK>
To   <>
Subject   Re: st: Strate-confidence interval method
Date   Fri, 23 Feb 2007 16:55:13 +0100

Milly wrote:
I want to calculate the variance from the confidence intervals given by
the command strate  (using no options).  I need the method that was used
to calculate these confidence intervals as it does not seem to be given
in the manual and it is hard to find the correct place in the ado file.
This is mentioned in stata list archives but with the SMR option
The manual is not very explicit although it does state (p. 216):
"By default, the confidence intervals are calculated using the quadratic
approximation to the Poisson log likelihood for the log-rate parameter."
I don't know it that is specific enough for you.
The returned results (not mentioned in the manual) include r(Var) and
r(sd) but I believe they describe the variation between strata.
An approximation to the standard error of the log(rate) would be:
(log(ciu) - log(cil))/3.92, but that may not be what you are asking for.
Instead of -strate- you might consider using -ci, poisson-.
Good luck,
Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6 
DK-8000 Aarhus C,  Denmark 
Phone, work:  +45 8942 6090 
Phone, home:  +45 8693 7796 
Fax:          +45 8613 1580 

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