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Re: st: Different sign in two model

From   Maarten buis <>
Subject   Re: st: Different sign in two model
Date   Sun, 12 Jul 2009 16:19:20 +0000 (GMT)

--- On Sun, 12/7/09, Maarten buis wrote:
> These two models model something different: the Weibull
> models the log hazard of experiencing the event, while 
> the log-logistic model the log time till the event. If
> the hazard is high then the time till the event should
> be small and vice versa, so you would expect the
> coefficients of the two models to have opposite signs.

You can get both models in the accelerated failure time
metric by specifying the -time- option in -streg- when
estimating the Weibull model.

A short discussion of these two metrics can be found
in section 4 of my introduction to survival analysis:

More can be found in:
Mario Cleves, William W. Gould, Roberto G. Gutierrez, 
and Yulia Marchenk (2008) An Introduction to Survival 
Analysis Using Stata, 2nd Edition. College Station, TX:
Stata Press.

Hope this helps,

Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen


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