[R] Why can repeated measures anova with within & between subjects design not be done if group sizes are unbalanced?

[Dieter Menne]

Charles C. Berry <cberry <at> tajo.ucsd.edu> writes:

> As the posting guide suggests, you could perform a search using
> 
> > RSiteSearch("repeated measures", restric="functions")
> 
> say.
> 
> That generates an inventory of functions that pertain to repeated 
> measures designs.

The problem I noted in practice with researcher is that  nlme is not among those
associated with "repeated measurements", with the exception of the citation of 

Davidian, M. and Giltinan, D.M. (1995) "Nonlinear Mixed Effects Models for
Repeated Measurement Data", Chapman and Hall.

somewhere in the nlme documentation. And as far as I remember, the word
"repeated measurements" cannot be found in text of Pinheiro & Bates; which
otherwise is the most worn-out book on my shelf.

I may be slightly off with both statements, but the association (mixed model)
<=> (repeated measurements) is not at all obvious. 

For the record: forget repeated measurements. It definitively pays to be fluent
in mixed models. Once you have your data in the "long" form, most work is done.
And if lme tells you it cannot solve your problem, it has damned good reasons
for it.

Dieter