[R] Power analysis for glm-function

simone sh13 at gmx.ch
Fri Jul 13 23:31:27 CEST 2007

Hello everybody

I have done a generalized linear model (glm-function) with a binary  
response variable (presence/absence) and two explanatory variables  
(including the interaction term (model<-glm(x~factor1*factor2,  
family=quasibinomial)). The interaction is what we are mainly  
interested in and it is non-significant (F=0, p=1.0). A reviewer on  
the manuscript now asks for a a priori power analysis on the non- 
significant interaction to see what sort of effect size we could  
reasonably have detected with our experimental design. As far as I  
have seen there is no power analysis function implemented for glm in  
R, or am I mistaken? Or does any one have any other suggestions how  
to deal with that comment?

I would really appreciate your help!
Thanks in advance


Simone Haerri
Institute of Environmental Sciences
University of Zurich
Winterthurerstrasse 190
Ch - 8057 Zurich

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