[R-sig-ME] is multicollinearity of fixed effects resolved by random effects

Reinhold Kliegl reinhold.kliegl at gmail.com
Tue May 20 09:50:21 CEST 2008

Two additions to my previous comment:

> Finally, you specify various random-effects parts and try to
> understand what they mean (see previous posts to this list), for
> example:
> (1|SITE)
> (1|GENUS)
> (1|GENUS) + (1|SITE)
> (1|GENUS) + (1|GENUS:SITE)   equivalent to  (1|GENUS/SITE)
If there are no big discrepancies in goodness of fit between two
plausible random-effects specifications, go with the representation
that makes best sense theoretically to you. Usually, they do not make
a difference for the fixed-effects part anyway. People subscribing to
this list should get away from simply looking for the smallest or
largest value of something.

I forgot: Check the residual distribution of the final model.

Reinhold Kliegl

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