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st: RE: RE: survival data analysis- recode survival time variable


From   Garry Anderson <g.anderson@unimelb.edu.au>
To   statalist@hsphsun2.harvard.edu
Subject   st: RE: RE: survival data analysis- recode survival time variable
Date   Tue, 25 Aug 2009 09:36:05 +1000

Maybe it is time to consider making Efron's method the default method.
Cleves et al (2008) say on page 151 with respect to Efron's method "This
approximation is more accurate than Breslow's approximation but takes
longer to calculate." With today's computing power this difference in
calculation time between the two methods may be very small. I would
prefer a more accurate approximation by default.

Cleves M et al (2008) "An Introduction to Survival Analysis Using Stata"
2nd Ed. Stata Press, TX.

Regrads, Garry
Garry Anderson
School of Veterinary Science
University of Melbourne
250 Princes Highway    Ph  03 9731 2221
WERRIBEE    3030       Fax 03 9731 2388
Email:  g.anderson@unimelb.edu.au

 

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Kieran McCaul
Sent: Tuesday, 25 August 2009 7:58 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: RE: survival data analysis- recode survival time variable

...

Also note, if you are doing a survival analysis where time is measured
in months, this may increase the proportion of tied failure times.  If
you are intending to use Cox proportional hazards regression for your
analysis, these ties need to be broken and the default method used is
Breslow's which may not be quite accurate if the proportion of ties is
large.  So you should check out the other options available in -stcox-:
Efron's Method or the exact methods. 

______________________________________________
Kieran McCaul MPH PhD
WA Centre for Health & Ageing (M573)
University of Western Australia
Level 6, Ainslie House
48 Murray St
Perth 6000
Phone: (08) 9224-2701
Fax: (08) 9224 8009
email: Kieran.McCaul@uwa.edu.au
http://myprofile.cos.com/mccaul
http://www.researcherid.com/rid/B-8751-2008
______________________________________________
If you live to be one hundred, you've got it made.
Very few people die past that age - George Burns

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Johannes
Schoder
Sent: Tuesday, 25 August 2009 4:57 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: survival data analysis- recode survival time variable

Hi,

I am working with survival data and have the problem that my variable
survival time is in the following format:
yymm, where y represents years and m months. Instead of the yymm format
I just want to have it in months since otherwise I always have the jump
from 11 months (0011) to 1 year (0100).

Thank you very much for your help!
Johannes
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