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Re: st: RE: Power calculation for ZINB and Poisson Models


From   Chris Ansen <lakridstina@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: RE: Power calculation for ZINB and Poisson Models
Date   Wed, 1 May 2013 10:37:03 +0200

Thank you Graeme.

I can now do a simulation fitted to my data. However the link you
refer to does not explain how to convert the simulated model (or
several simulated models) into a power estimation.

Anybody who knows how to do that??? I would really appreciate your input.

Kind regards
Christina

On Tue, Apr 30, 2013 at 11:05 AM, MacLennan, Graeme
<g.maclennan@abdn.ac.uk> wrote:
> Christina, I will not comment on code below, but instead suggest this post which covered ZINB simulation.
>
> http://www.stata.com/statalist/archive/2011-11/msg00748.html
>
> HTH. Graeme.
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Chris Ansen
> Sent: 30 April 2013 08:16
> To: statalist@hsphsun2.harvard.edu
> Subject: st: Power calculation for ZINB and Poisson Models
>
> Dear all
>
> I am trying to do a power calculation with simulated data. Originally I wanted to do one for a zero-inflated negative binomial model, testing three null hypothesis as suggested by Williamson et al. "Power Calculations for ZIP and ZINB Models", Journal of Data Science 2007.
> It is found easily by typing the title to a Google browser. Here three null-hypotheses are tested:
>
> Three null-hypotheses:
> H0: lamda1 equals 0                      nbreg-part of the model
> H0: beta1 equals 0                         logistic part of the model
> H0: [beta1, lamda1] equals [0,0]      joined logistic and nbreg
>
> However I started with simulation of the simpler Poisson inspired by:
> http://www.stata-journal.com/sjpdf.html?articlenum=st0010
> and
> http://www.stata.com/support/faqs/statistics/power-by-simulation/
>
> My problem is that even though I copy the two different approaches and execute them - both gets stuck by the command "generate x =`d1´ in 1 with the error message "in not found" r(111);
>
> The commands looks like this:
> args N r d1 d2 d3 b1
> drop _all
> set obs 3
> generate x =`d1´ in 1
> and continues exactly as explained in the link
>
> The other rather long approach (see link under Poisson with a loop within a loop) - does not work either! I am using STATA SE 11.2
>
> Both examples are copied from the two mentioned links, the only thing I have changed is the `var´, because they copy differently. I have also changed them for this mail not to be bounced from statalist.
>
> I have tried the long approach with version 7.0, 11.0 and 11.2 - so this is not the case.
>
> I will welcome any advises and solutions - also a more simple approach is very welcome.
>
> Thank you for your precious time.
>
> Kind regards
> Christina
>
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