hello marten,
thanks for the hint. that seems to the right model. i tried to use the
ztnb but stata gives the error message that convergence could not be
achieved. on the ucla stata page is a warning that the method might be
problematic with a small sample, but it is unclear what is a small
sample. i have 180 observations. do you have any idea how to get the
regression running?
in some instances, i create a percentage variable of negative coverage
once coverage is received. for that i am able to poisson now.
however, the problem with the at 1 trunctated count variable and
stata's error message that convergence could not be achieved persists.
thank you for your help
peter
2008/3/24, Maarten buis <[email protected]>:
> --- "Peter F. Schmidt" <[email protected]> wrote:
> > my variable is overdispersed, ruling out poisson, and as it is
> > conditioned on that at least one article is written, i do not have
> > zero values.
>
>
> Have a look at -help ztp- and -help ztnb-.
>
> Hope this helps,
> Maarten
>
> -----------------------------------------
> Maarten L. Buis
> Department of Social Research Methodology
> Vrije Universiteit Amsterdam
> Boelelaan 1081
> 1081 HV Amsterdam
> The Netherlands
>
> visiting address:
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>
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>
> http://home.fsw.vu.nl/m.buis/
> -----------------------------------------
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