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From |
Maarten buis <[email protected]> |

To |
[email protected] |

Subject |
Re: st: ST: Hazard rates translating into probabilities |

Date |
Wed, 23 Jan 2008 10:05:58 +0000 (GMT) |

--- Michael Kregar <[email protected]> wrote: > I have run the following cox proportional regression > How can I obtain an overall probability of the above > model when using data from say one observation (for > the four independent variables above). I am looking > for overall probabilities of failure (not hazard > rate). Can anyone give me a one by one calculation? This can be interpreted in two ways: 1) you want to probability of failure as an end result (at t=infinity). In most parametric models (-streg-) this is easy: that probability is 1 for everyone. So called cure models explicitly allow for a given proportion of observations that will never experience the event (are "cured"). I am not so sure if a Cox model makes any statement about what hapens at t=infinity. I could imagine that it either leaves that undefined or that it assumes that in the end everybody dies. I find it implausable that you could derive a curefraction from a Cox model. For more on cure models in Stata see (Lambert 2007). 2) A more interesting way to interpret your question is to assume that you are asking for 1-Survivor function, i.e. the probability that someone has died at or before some specific timepoint. You can compute those as in the example below. More interestingly (and easy) you can plot them using the -stcurve- command (see: -help stcurve-). *--------------- begin example ------------------ sysuse cancer, clear stset studytime, failure(died) xi: stcox i.drug age, basesurv(base) predict double xb, xb gen S = base^exp(xb) *---------------- end example ------------------- (For more on how to use examples I sent to the Statalist, see http://home.fsw.vu.nl/m.buis/stata/exampleFAQ.html ) Lambert, Paul (2007) "Modeling of the cure fraction in survival studies". The Stata Journal, 7(3), pp. 351-375. Hope this helps, Maarten ----------------------------------------- Maarten L. Buis Department of Social Research Methodology Vrije Universiteit Amsterdam Boelelaan 1081 1081 HV Amsterdam The Netherlands visiting address: Buitenveldertselaan 3 (Metropolitan), room Z434 +31 20 5986715 http://home.fsw.vu.nl/m.buis/ ----------------------------------------- __________________________________________________________ Sent from Yahoo! Mail - a smarter inbox http://uk.mail.yahoo.com * * 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/

**References**:**st: ST: Hazard rates translating into probabilities***From:*Michael Kregar <[email protected]>

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