[R] question about warning message in nlme model

[Christine Calmes]

I am writing to inquire about a warning message that I receive when 
trying to model a random slope and intercept at the second level of a 
3-level model.  Specifically, I am testing a 3-level model in which 
time (WEEK) is nested in participants (PARTICIP) and participants are 
nested in dyads (DYADID). The goal is to examine how an interpersonal 
style (CORUMTO) one week predicts changes in depression the following 
week (BDIAFTER) controlling for levels of depression (BDI) from the 
previous week.  I have approximately 80 dyads and approximately 160 
participants.

When modeling a random slope and intercept at the second level (the
participant or person level), I receive output, and I also receive the
following error message.

Warning message
Fewer observations than random effects in all level 2 groups

I was wondering what this error message means and if it may be 
suggesting that the results after the summary statement are incorrect.

I also want to verify that the following syntax is appropriate for
modeling a random intercept and slope on the variable CORUMTO at the
participant level and a random intercept and fixed slope at the dyad 
level.

intercept<-lme(BDIAFTER~BDI+WEEK+CORUMTO, random=list(DYADID=~1, 
PARTICIP=~CORUMTO), data=weeklydata)

Any help you can give would be much appreciated.

Thank you for your time.

Sincerely, 
Christine Calmes

Christine Calmes, M.A.
Doctoral Candidate, Clinical Psychology
University at Buffalo: The State University at New York
Department of Psychology; Park Hall
North Campus
Buffalo NY, 14260