Re: st: R: compare median survival times? (flag: Stata 9.2/SE)

[Ronan Conroy <rconroy@rcsi.ie>]

On 11 Meith 2010, at 08:44, Carlo Lazzaro wrote:

> Marty may want to customize what follows:
> --------- code begins-----------
> sysuse cancer.dta, clear
> stset studytime, failure(died==1)
> sts test drug if r(p50), logrank
> -------- code ends---------------

But doesn't this just compare the survival function in those in whom  
the median survival time is definable?

The hypothesis is a very peculiar one indeed: specifically, that the  
50th percentile of the survival function differs between two groups. I  
don't know why anyone would formulate this hypothesis (why the 50th  
centile and not some other quantile? why ignore differences at other  
quantiles?) but it's a tricky one to try to test. It seems to me that  
you would need interval quantile regression, something whose  
complexities cause one to have to sit down and drink a glass of water.

Or am I missing something?


Ronan Conroy
=================================

rconroy@rcsi.ie
Royal College of Surgeons in Ireland
Epidemiology Department,
Beaux Lane House, Dublin 2, Ireland
+353 (0)1 402 2431
+353 (0)87 799 97 95
+353 (0)1 402 2764 (Fax - remember them?)
http://rcsi.academia.edu/RonanConroy

P    Before printing, think about the environment




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