effect size / linear mixed effects models

[Wilbert0]

Hi all,

 

I want to measure  the effect size for each of the fixed factors in a linear mixed effects models analysis. SPSS gives for each of the fixed factors an F. Is it OK to measure to measure the effect size per factor as follows:

 

R-square = F / (F + Denominator df)

 

Best regards,

 

Wilbert