On Aug 3, 2010 9:43am, Sam <Sam_Smith@me.com> wrote:
> Dear Dan,



> Thanks for this,



> I was not working back from the AIC i was just unsure why they are  
> different - in what way are they a different model?



> If i have categorical predictors i should code them as factors in GLMM -  
> correct?



> Thanks


Yes, they should be coded as factors. Otherwise you will be fitting a  
linear model -- ie, R
will assume that the change in the response is the same between any two  
consecutive levels.
The only situation where it doesn't matter is with a categorical variable  
with only two levels.
In general if you have factors coded with meaningful labels you should  
leave them that way
rather than recoding as numeric, both to avoid this kind of confusion and  
because you
then don't have to spend brainpower remembering which numeric code  
corresponds to
which level ...

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