Effect Size in lme

Dear Ben,
Many thanks.

Thanks for clarifying: yes, I am interested in effect size with  
respect to biological significance of my findings.  In addition to  
the suggestions you have provided, which I hope to talk to you some,  
would you recommend using the following formula, from Nakagawa &  
Cuthill (2007) Biol. Rev. 82, 591-605: partial correlation  
coefficient, r = the t value divided by the square of the sum of the  
t value squared and its corresponding degrees of freedom?

Here is the equation:


I am not quite sure how to interpret, with respect to the kind of  
effect I am looking for, the parameter estimates and the other values  
that you suggested. Are there resources you can recommend. In the  
meantime, I will check in P & B 2000 as well as in West et al. 2007.

Thanks,
Patrick

Patrick Onyango wrote:

All,
I have been asked to provide effect sizes for results I obtained from
lme. Does anyone know how to handle this?

Many thanks already.
Patrick

  There are a lot of definitions of "effect size".  If the request is
simply to indicate the practical relevance of the effects (i.e.
'biological' significance), I would just quote the parameter estimates
(with standard errors), and the standard deviations of the random
effects ...

-- 
Ben Bolker
Associate professor, Biology Dep't, Univ. of Florida
bolker at ufl.edu / people.biology.ufl.edu/bolker
GPG key: people.biology.ufl.edu/bolker/benbolker-publickey.asc