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From |
Maarten Buis <maartenlbuis@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: log normal and logistic hazard ratio |

Date |
Mon, 20 Jun 2011 08:37:44 +0200 |

On Mon, Jun 20, 2011 at 4:42 AM, Yusvita Triwiadhian S. wrote: > Lognormal and logistic distribution for survival anlysis,there isn't > hazard ratio,is it right? why? i'm looking for command to get its > hazard ratio but i do not get it.. Because a hazard ratio are only reported in models that make the proportional hazard assumption, and both the lognormal and the loglogistic only work with the accelerated failure time metric. In models that make the proportional hazard assumption you have a baseline hazard function that says how high the hazard is at each point in time for someone that has all zeros on his/her explanatory variables. The proportional hazard assumption implies that the hazard function of all other groups only differ from the baseline hazard function by a fixed proportion. If we did not make that assumption than our effect of a variable would differ depending on how much time the individual has been at risk. It is thus because of this assumption that we can summarize the effect in one number. Alternatively, if we want to relax the proportional hazard assumption we can add interaction terms with analysis time and thus let the effect change with time, as I proposed here: <http://www.stata.com/statalist/archive/2011-06/msg00358.html> In accelerated failure time models like the lognormal and loglogistic the idea is that times goes faster for some types of individuals than others (e.g. one year for a dog is equivalent for 7 years for humans). Again there is a baseline function, but now the explanatory variables influence the time axis instead of the hazard. Hope this helps, Maarten -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: log normal and logistic hazard ratio***From:*"Yusvita Triwiadhian S." <07.5544@stis.ac.id>

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