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Re: st: multile comparison among incidence rates

From   "Svend Juul" <SJ@SOCI.AU.DK>
To   <>
Subject   Re: st: multile comparison among incidence rates
Date   Thu, 3 Apr 2008 17:56:00 +0200

Carlo wrote:
I would like to compare three incidence rates (the only effectiveness end
point available) concerning three group of patients with the same disease,
treated with three different drugs and followed-up for six months.
Is there any way to do it in Stata/SE 9.2? Is there any reference about your
It is not quite clear to me what you mean by "compare three incidence
rates". Is it a question of significant difference or estimation of
incidence rate ratios or rate differences? And do you want to compare
B vs A and C vs A only, or do you also want to compare B vs C?
Below I used -ci- to estimate the individual incidence rates and
-poisson- to estimate incidence rate ratios (imagine that -agecat-
represents the drugs to be compared).
    webuse dollhill3.dta
    by agecat, sort: ci deaths, poisson exposure(pyears)
    xi: poisson deaths i.agecat, exposure(pyears) irr
Hope this helps

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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