Hi, all,

I have a dataset with several individuals from different sites measured 
several times. There are 7 different sites and around 10 individuals 
from each site. My question is:

Is this what Douglas Bates call "implicit nesting"? If so, the recommendation is to create a new variable

data<- within(data, {siteid<- factor(site:id)}

And the model specification...

fm1<- lmer(y ~ x1 + x2 + (1|siteid), data)

which seems to be identical to

fm2<- lmer(y ~ x1 + x2 + (1|site:id)), data)

What is the difference between the specifications above and

fm3<- lmer(y ~ x1 + x2 + (1|id) + (1|site), data)

I get identical results from models fm1 and fm2, but slightly different 
results from fm3.


Thanks,

Gustavo S. Betini
PhD student
Dept. of Integrative Biology
University of Guelph, Canada





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