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# st: Power calculation for ZINB and Poisson Models

 From Chris Ansen To "statalist@hsphsun2.harvard.edu" Subject st: Power calculation for ZINB and Poisson Models Date Tue, 30 Apr 2013 09:16:17 +0200

```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

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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```