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st: STCOX survival estimates and SEs with shared Frailty

From   "Cameron L. Aldridge" <>
Subject   st: STCOX survival estimates and SEs with shared Frailty
Date   Sat, 05 Feb 2005 18:55:31 -0700

For All those Survival Analyses Experts out there.......

I am estimating a cox proportional hazards model, to look at survival of young birds (chicks). In many cases, I have multiple individual chicks with a brood marked and followed, but they are not independent of each other. Thus, I estimating a shared frailty model as follows:

stcox X1 X2 X3, shared (Brood_num)

Where the X's are my covariates, and Brood_num is a unique identifier for the specific brood of chicks.

However, I can not figure out how (if I can) generate an appropriate survival or hazard function, that correctly estimates the SE (& Confidence Intervals) associated with the cumulative function (i.e. based on the latent effect of chicks within broods).

I can only seem to revert back to the basic K-M function, and possibly use a robust cluster for Brood_num to inflate my SE on my survival/hazard function.

Is there any way to appropriately account for the covariance of multiple chicks within a brood, and correctly estimate the survival function and SE's based on the shared frailty within Broods?

I have searched the lsitserv archives, but had any luck!


Cameron L. Aldridge
Department of Biological Sciences,
University of Alberta
Edmonton, AB T6G 2E9
Voice: (780) 492-6267 Fax: (780) 492-9234

Field Address: Box 112 Manyberries, AB T0K 1L0
Voice/Fax: (403) 868-2025

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