[R] Post hoc power analysis for mixed-effects models

[David Winsemius]

On Jun 4, 2013, at 4:46 PM, Kota Hattori wrote:

> Dear all,
>
> I have been searching ways to run power analysis for mixed-effects  
> models. However, I have not been successful
> in the research. Today I would like to ask your help. As long as I  
> see from my search, Martin Julien wrote a package
> called pamm for the power analysis. One of the limitations in the  
> current version is that pamm cannot handle
> categorical fixed variables. Todd Jobes introduced his script to run  
> power analysis for mixed-effects models
> (http://toddjobe.blogspot.co.nz/2009/09/power-analysis-for-mixed-effect-models.html 
> ). However, some parts of
> the script is beyond my knowledge. I am not sure if I can run power  
> analysis with categorical variables either. Is there
> anybody who has run post hoc power analysis for mixed-effects  
> models? If you have experiences, I would like to
> ask your help. Thank you very much for taking your time.

Can you provide a sensible justification for "post hoc power analysis?  
I know the terminology has crept into widespread use due to its  
existence in either SAS or SPSS (I forget which), but I have doubts  
about its validity. It mixes up the order of statistical testing  
logic. Power analysis is something done _before_ the study. If a  
statistical procedure is done after a study's data is collected with  
the very dubious assumption that the sample statistics are the  
population statistics, it's not a power analysis.

-- 
David Winsemius, MD
Alameda, CA, USA