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st: RE: calculating relative risk

From   "Silcocks Paul" <[email protected]>
To   <[email protected]>
Subject   st: RE: calculating relative risk
Date   Fri, 7 Dec 2007 13:01:19 -0000

With a low risk in the first place, the odds ratios will be a good
approximation to the relative risk, but if you do want to model relative
risk you'd be better off using a Poisson family with log link (or do it
more economically with a Poisson regression).  Use the robust variance
option and you should solve your problem.  See Guangyong Zou "A modified
Poisson regression approach to prospective studies with binary data" Am
J Epidemiol (2004) 159: 702-706

Paul Silcocks BM BCh, MSc, FRCPath, FFPH, CStat Clinical Senior Lecturer

Nottingham Clinical Trials Support Unit
Room B39 
School of Community Health Sciences 
University of Nottingham Medical School 

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-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Sue Kim
Sent: 04 December 2007 22:46
To: [email protected]
Subject: st: calculating relative risk

Hi. I have a binary outcome where the probability of outcome is low so I
want to get an adjusted relative risk (rather than odds ratio) using
glm.  When using glm with fam(bin) link(log) command, I get a warning
"parameter estimates produce inadmissible mean estimates in one or more
observation". Could I still use the results or is there a way to get
around this problem?
Thank you.

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