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From |
Fred Wolfe <fwolfe@arthritis-research.org> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Margins command after Cox regression |

Date |
Fri, 30 Dec 2011 08:36:58 -0600 |

Thanks, Maarten. Fred On Fri, Dec 30, 2011 at 8:13 AM, Maarten Buis <maartenlbuis@gmail.com> wrote: > On Fri, Dec 30, 2011 at 1:46 PM, Fred Wolfe wrote: >> I am trying to get margins expressed in probability units rather than >> hazard ratios after Cox regression (Stata 12). > > I don't think you can. First, it is hard to define the probability in > the context of a survival analysis. Is it the probability of the event > occuring at time = 0 or at the end of the study or somewhere in > between? Second, even after you have defined what probability you > want, it is still the aim of Cox to make such statements hard. That is > not because Cox(*) is such a nasty person, but because he avoided > making assumptions on the baseline hazard and by avoiding such > assumptions it prevents you from making wrong assumptions. However, > the price you'll have to pay is that it is only a useful model if you > want to make statements on relative quantities, like the hazard ratio, > and it becomes very hard to make statements on absolute quanitties > like the hazard or the probability. That is a logical consequence of > not estimating the baseline hazard, so there is not much that can be > done about that. > > Hope this helps, > Maarten > > (*) David not Nick > > -------------------------- > 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/ * * 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/

**Follow-Ups**:**RE: st: Margins command after Cox regression***From:*Cameron McIntosh <cnm100@hotmail.com>

**References**:**st: Margins command after Cox regression***From:*Fred Wolfe <fwolfe@arthritis-research.org>

**Re: st: Margins command after Cox regression***From:*Maarten Buis <maartenlbuis@gmail.com>

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