On 14.02.2010 21:20, Benjamin Cheah wrote:
Hi all,

I've been struggling with trying to specify a diagnoal matrix for linear mixed 
effects model. I think I've got nearly everything correct, except the following 
message appears:

In lme.formula(fixed = fwave ~ sex + sexXbulbar + visit + age +  :
   Fewer observations than random effects in all level 1 groups

Not sure if i've provided enough details, but I'm basically trying to perform a 
mixed effects model analysis, controlling for several covariates. Incorporating 
random effects for the intercept and slope.

What does the second line, 'Fewer observations than random effects in all level 
1 groups' mean?

That your data is lacking degrees of freedom? In short: You need at least one observation for each parameter estimate to be able to estimate any coefficients, and you need much more in order to get sensible results. Hence you need either more data or need to estimate less parameters.

Best,
Uwe Ligges




Many thanks in advance,

Ben Cheah



       
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