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From |
Lars Kroll <lars@climweb.de> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: stset and the NLSY97 |

Date |
Mon, 17 Oct 2005 09:24:23 +0200 |

I don't think your on the right way Marcello, id year age firstsex_yr > > 1 1997 15 . > > 1 1998 16 16 > > 1 1999 17 16 > > 1 2000 18 16 > > 2 1997 12 . > > 2 1998 13 . > > 2 1999 14 11 > > 2 2000 15 11 > > 3 1997 16 12 > > 3 1998 17 12 > > 3 1999 18 12 > > 3 2000 19 12 are single failure multiple obs per subject data, so I would suggest: gen failure = age==firstsex if firstsex<. sort persnr year by persnr, sort : gen enterstudy = year==year[1] // if your first year // isn't 0 one never // know... stset age, id(id) failure(failure==1) exit(failure==1) enter(enterstudy==1) Hope this helps, Lars Am Sonntag, den 16.10.2005, 21:46 -0400 schrieb Marcello Pagano: > I do not understand your dilemma. Assuming everyone is telling the truth, > what you seem to have is time to first sex is your outcome of interest with > the very Victorian identification of "death" as that time. If someone is 17 > at the time of the survey without having had sex, then that is a censored > observation. So your "time" variable is firstsex_yr if sa==1 > and age if sa==0. So you need to generate a variable > > gen time = age > replace time = firstsex_yr if sa==1 > stset time , failure(sa) > > Your hazard should be zero for time < = 10, but that > depends on your data. You actually do have information back then, assuming > you have done a decent job of sampling and things have not changed > that much over the years. (By that I mean that if everyone you question > is over 12, say, then their experience in the 0 to 12 time period is > still representative of what is going in those years today.) > > Hope this helps, > > m.p. > > Scott Cunningham wrote: > > > On Oct 16, 2005, at 9:01 PM, Nick Cox wrote: > > > >> Not my field, but your dummy calculation can > >> be put more succinctly: > >> > >> gen sa = firstsex_yr <= age > >> > >> However, safer would be to trap missings: > >> > >> gem sa = cond(mi(firstsex_yr, age), ., firstsex_yr <= age) > >> > >> Nick > > > > > > Nick, > > > > Thanks for helping make the dummies more succinct. > > > > Do you think, though, that it is correct to use "age" as the actual > > duration variable? So, for instance, I have a long dataset like this: > > > > id year age firstsex_yr > > 1 1997 15 . > > 1 1998 16 16 > > 1 1999 17 16 > > 1 2000 18 16 > > 2 1997 12 . > > 2 1998 13 . > > 2 1999 14 11 > > 2 2000 15 11 > > 3 1997 16 12 > > 3 1998 17 12 > > 3 1999 18 12 > > 3 2000 19 12 > > > > So, by stsetting the data as so: > > > > . stset age, failure(sa) > > > > where "sa" is an indicator equalling "1" if the person has become > > sexually active (signalling "death" in this context) and 0 > > otherwise. If I stset the data such that "age" is the duration, have > > I really made the right decision? Or should I use "year" or should > > have some other variable that I create to correspond to time that has > > passed? Because I really want to look at ten periods, initially - > > from 10 years to 19 years of age. It's a short duration, relatively > > speaking, and most "exits" occur at 15-17. So I don't actually have > > data for resopndents for those early, pre-survey, ages - ie, 10-12. > > So what's the best solution here? Do I create a variable, maybe > > "time" or "virgin_time", that takes on a value of 1 to 10, and that > > variable matches up to the years that are covered in the data, and > > the years not covered? > > > > Is this post making sense? I'm mainly just not sure of the proper > > way to execute this stset command to make use of the information I > > have in the form I currently have it in. > > > > > > scott > > * > > * For searches and help try: > > * http://www.stata.com/support/faqs/res/findit.html > > * http://www.stata.com/support/statalist/faq > > * http://www.ats.ucla.edu/stat/stata/ > > * > * For searches and help try: > * http://www.stata.com/support/faqs/res/findit.html > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ -- Lars E. Kroll Tutor für EDV & Statistik Institut für Soziologie Freie Universität Berlin KONTAKT: Email mail@lkroll.de Website www.lkroll.de * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: RE: stset and the NLSY97***From:*Scott Cunningham <scunning@gmail.com>

**Re: st: RE: stset and the NLSY97***From:*Marcello Pagano <pagano@hsph.harvard.edu>

**References**:**st: RE: stset and the NLSY97***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

**Re: st: RE: stset and the NLSY97***From:*Scott Cunningham <scunning@gmail.com>

**Re: st: RE: stset and the NLSY97***From:*Marcello Pagano <pagano@hsph.harvard.edu>

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