[R] a priori power analysis for glm, family = poisson

Joerg Luedicke joerg.luedicke at gmail.com
Wed Feb 20 20:36:36 CET 2013

Probably the best way of doing this is via simulation. Have a look at
chapter 5 of:

Bolker, B. 2008. Ecological models and data in R. Princeton Univ. Press,
Princeton, NJ.

for an introduction and a bunch of examples.


On Wed, Feb 20, 2013 at 5:49 AM, Chad Widmer <cw647 at st-andrews.ac.uk> wrote:
> Dear R/statistics wizards,
> This may be more of a statistics question than an R one, but I’m hoping
> that someone has the time to help.  I’ve already consulted a few local
> statisticians and I’ve not yet received a clear answer.  Before I start an
> experiment I want to conduct an a priori power analysis test for a
> Generalized Linear Model, family = poisson.  The response variables will be
> counts.  I want to look at the effects of 5 temperatures and 3 salinities,
> and their interaction in 15 different combinations (5 temperatures each
> testing 3 different salinity levels).   I am hoping to learn the power I
> would achieve if I used a sample size of 18 in each of the combinations,
> for a total sample size N = 270.
> Does such a power analysis exist?  Can I just use a power analysis for a
> linear model since the glm is an extension of that (which seems to make
> sense), or maybe even one from a 2 way anova? Can someone show me the path
> of righteousness in R, or point me in the right direction please?
> Thank you very much for your valuable time.
> Chad
>         [[alternative HTML version deleted]]
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