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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 * * 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: Left truncation in survival analysis***From:*Austin Nichols <austinnichols@gmail.com>

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