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Re: st: Left truncation in survival analysis


From   Steven Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Left truncation in survival analysis
Date   Thu, 28 Apr 2011 11:32:44 -0400

Yigit-

Actually, there is an approach to left-truncation when start times are not known. It is outlined Wooldridge (2002), pp 703 & 718 (problem 20.8).  This approach requires a parametric model for the distribution of the unobserved starting times. It is not implemented in Stata.

In addition to describing this problem as one of "left-truncation", Wooldridge also uses the term "left censoring".  I believe that this usage is incorrect.  

Reference: Wooldridge, Jeffrey M. 2002. Econometric Analysis of Cross Section and Panel Data. Cambridge, Mass.: MIT Press.  (There is also a 2010 edition of this fine book.)

Steve
sjsamuels@gmail.com






You are welcome, Yigit.  

In Statalist, a  private thank you note is always appreciated, not only by the recipient but by others for whom it's not informative.  I am forwarding your post to the list because there is still a substantial issue.

But no, the name of your phenomenon *is* left truncation. Left censoring occurs when you know for some individuals only that the event took place prior to a certain time.  An early article that addressed this phenomenon was: Wagner, S.S., and S.A. Altmann. 1973. What time do the baboons come down from the trees? (an estimation problem). Biometrics 29 (4): 623-635.   On some mornings, the observer arrived too late to see what time the baboons descended.


Steve
sjsamuels@gmail.com

On Apr 28, 2011, at 8:42 AM, Yigit Aydede wrote:

Hi Steve,

Thanks a lot for your response.  And thanks for the reference.  I guess the name of my problem is left-censoring. I checked it in the literature and I saw different definitions for it.  There are some suggested solutions to it, but I am not sure if they are robust enough.  Some say left-censoring can be treated as interval censoring (An Introduction to Survival Analysis Using Stata - Cleves et al).  I guess I need to read more.  

Sorry for writing this directly to you but I don't know how to response your e-mail by using Statalist.

Best,
--Yigit   

Yigit Aydede
Department of Economics
Sobey School of Business
Saint Mary's University
Halifax, Nova Scotia, B3H 3C3
Canada
T (902) 420.5673
F (902) 420.5129




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