[R-lang] Contrast coded mixed models: Interactions

[Peter Graff]

Dear R-Langs,

I'm currently trying to analyze some experimental data with a contrast 
coded mixed model. I have a 2 (levels:A,B) x 3 (levels:D,E,F) design 
with unbalanced cell sizes. I am coding the following variables:

AvB, DvE, EvF

where sum(AvB)=0, sum(DvE)=0, sum(EvF)=0. Next I fit this model:

lmer(DV~AvB*(DvE+EvF)+(1|Subj)+(1|Item))

And here is the correlation matrix it outputs:

Correlation of Fixed Effects:
                  (Intr)   AvB    DvE     EvF  AvB:DvE
AvB         -0.029                            
DvE          0.010 -0.006                     
EvF         -0.002 -0.001  *0.488  *            
AvB:DvE -0.003  0.015 -0.039 -0.018       
AvB:EvF -0.001 -0.002 -0.018 -0.044  *0.488 *

The question I have is, how to get rid of the collinearity in red and 
blue and whether it's even possible. And if it's not possible, in what 
way will this affect the reliability of my result?

Thanks so much in advance,

Peter
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