Monday, January 02, 2006

RE: st: Survival analysis: Interpretation of Cox regression

> > 2) How can I verify if survivor function at a particular time > > (e.g. 5 years) are statistically different? > > It is an assumption of the Cox model that the hazard of group one is always proportional to the > hazard of the reference category. So if you find a hazard ratio of 1.4, than the hazard of group > one is always 40% higher than the hazard of the reference category. If this effect is significant > than the groups are, by assumption, always significantly different.

More about testing the proportionality assumption can be found on: http://www.ats.ucla.edu/stat/sas/faq/test_proportionality.htm and http://www.ats.ucla.edu/stat/stata/seminars/stata_survival/default.htm

HTH, Maarten

----------------------------------------- Maarten L. Buis Department of Social Research Methodology Vrije Universiteit Amsterdam Boelelaan 1081 1081 HV Amsterdam The Netherlands

visiting adress: Buitenveldertselaan 3 (Metropolitan), room Z214

+31 20 5986715

http://home.fsw.vu.nl/m.buis/ -----------------------------------------

* * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/


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