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Re: st: RE: Poisson Regression

From (Brendan Halpin)
Subject   Re: st: RE: Poisson Regression
Date   Mon, 14 Feb 2011 22:35:51 +0000

On Mon, Feb 14 2011, Visintainer, Paul wrote:

> It is an issue of interpretability -- and I wouldn't think that
> clinicians would find the issue trivial. In their response to letters
> following publication of "What's the relative risk?" (Zhang & Yu, 1998.
> What's the Relative Risk, JAMA, Vol 280, No 19, pp 1690-1691), Zhang &
> Wu intimate that clinicians are likely to sacrifice a little precision
> (and perhaps validity?) for something that is simple and interpretable.

Relative rates are simple and interpretable, but if the base rate
differs substantially among sub-populations, they are incoherent. If one
sub-population has a base rate of 5% and another 40%, for instance, a
relative rate of two in each case (5% to 10%, 40% to 80%) would
represent extremely different processes (in one case turning 1 of 19
noes to yes; in the other 2 of 3).

This is why I say the relative rate is only superficially intuitive --
it seems like a natural measure of effect but it is not robust.



PS: At least some of the functionality of -margins- must be incorporated
in other stats packages, surely?
Brendan Halpin,  Department of Sociology,  University of Limerick,  Ireland
Tel: w +353-61-213147 f +353-61-202569 h +353-61-338562; Room F1-009 x 3147
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