[R-sig-ME] Running repeated measures in lme4

[Emma Stone]

Dear all,

I wander if you can help.

I am running a repeated measures model with lmer.I have 8 sites, at each I 
conducted an experiment with treatments which have 4 levels. Each treatment 
was conducted only once per site, but each site has one of each of the 
treatment levels so it is balanced. Obviously the treatments within sites 
are the repeated measures component, and I want to look at differences 
between treatments within sites, I am not really interested in the site 
group effect but need to incorporate it. So I have set up my model as 
follows:

model1<-lmer~(minutes~treatment+(treatment|site), data = data)


But when I run the model, it gives no variance for the group level effect 
as shown below.

Random effects:
 Groups   Name        Variance Std.Dev. Corr
 site     (Intercept) 0.00000  0.00000
          treatment   0.00000  0.00000    NaN
 Residual             0.07707  0.27762
Number of obs: 32, groups: site, 8

Is this because I only have one replicate of each treatment level at each 
site? Can anyone help?

Thanks

Emma
University of Bristol