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RE: st: Perfect predictors of an occurrence (survival analysis)


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: Perfect predictors of an occurrence (survival analysis)
Date   Thu, 13 Mar 2008 12:54:55 +0000 (GMT)

Your data should look something like this

id t leave
1  1  0
1  2  0 
1  3  1
2  1  1
3  1  0 
3  2  0
3  3  0
etc.

In case of panel data this is often called long format, in case of
survival data this is often requires the use of -expand-. This is
discussed in detail in lecture 6 of:
http://www.iser.essex.ac.uk/teaching/degree/stephenj/ec968/

Hope this helps,
Maarten

--- Luis Ortiz <luis.ortiz@upf.edu> wrote:

> Dear Maarten,
> 
> Thanks for the quick response.
> 
> Initially, since I only have discrete time data, I was using cloglog,
> but,
> as I said, the analysis was... rejected, since type-of-contract
> dummies turn
> out to be perfect predictors of the outcome.
> 
> Thanks for your attention again
> 
> Luis Ortiz
>  
> 
> -----Mensaje original-----
> De: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] En nombre de Maarten
> buis
> Enviado el: jueves, 13 de marzo de 2008 13:38
> Para: statalist@hsphsun2.harvard.edu
> Asunto: Re: st: Perfect predictors of an occurrence (survival
> analysis)
> 
> What commands are you using?
> 
> --- Luis Ortiz <luis.ortiz@upf.edu> wrote:
> 
> > Dear Statalisters,
> > 
> > I'm analysing the occurrence of the following event: getting out of
> > employment if you are over-educated. I'm doing so for a number of
> > over-educated individuals, using panel data. The spells are the
> > periods in
> > over-education.
> > 
> > I am especially interested by the type of contract. This is one of
> my
> > main
> > independent variables. Therefore, I have split the initial variable
> > in the
> > corresponding dummies, in order to include them in the analysis.
> Yet,
> > I have
> > found that each one of these dummies perfectly predict the
> occurrence
> > of the
> > event I'm studying. It might be because the spells are not very
> long
> > and the
> > job, no matter how over-qualified it is, goes associated with a
> given
> > type
> > of contract. In other words, the type of contract does not change
> > during the
> > spell.
> > 
> > In such a case, dummy covariates on type of contract are not
> feasible
> > for
> > the analysis. They perfectly predict the occurrence of the event.
> > 
> > Yet, this does not mean that over-educated workers are equally
> likely
> > to get
> > out of employment REGARDLESS of their type of contract. Moreover, I
> > suspect
> > that the type of contract may be associated to a different
> likelihood
> > of
> > getting out of the employment.
> > 
> > How could I overcome the problem I have mentioned for running
> > survival
> > analysis? Is there any alternative way to estimate the relative
> > likelihood
> > of temporary / permanent over-educated workers quitting their jobs
> > that you
> > come up with?
> > 
> > I do appreciate your attention
> > 
> > Best regards
> > 
> > Luis Ortiz
> > 
> > *
> > *   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/
> > 
> 
> 
> -----------------------------------------
> Maarten L. Buis
> Department of Social Research Methodology
> Vrije Universiteit Amsterdam
> Boelelaan 1081
> 1081 HV Amsterdam
> The Netherlands
> 
> visiting address:
> Buitenveldertselaan 3 (Metropolitan), room Z434
> 
> +31 20 5986715
> 
> http://home.fsw.vu.nl/m.buis/
> -----------------------------------------
> 
> 
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> 


-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


      __________________________________________________________
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