[R] Validating a mixed-effects model

[Armin Goralczyk]

Hi

I constructed a mixed-effects model from longitudinal repeated
measurements of lab values in 22 patients seperated into two groups
with the groups as fixed effect using lme. I thought about using the
jackknife procedure, i. e., removing any one subject and calculating
the fixed effect, to assess the stability of the fixed effect and
thereby validate the model. I suppose this has been done in the
following study:

http://content.nejm.org/cgi/content/full/357/19/1903
(this may be restricted access, sorry)

Is such an approach feasible?

Also in the article results are confirmed by comparing the mixed model
with a fitted least-squares regression. I understand that this can be
achieved with lmlist, but only for for models without an additional
fixed effect!?

Are there any other good approaches to validate a mixed-effects model
that will be accepted in medical peer review?

-- 
Armin Goralczyk, M.D.
--
Universitätsmedizin Göttingen
Abteilung Allgemein- und Viszeralchirurgie
Rudolf-Koch-Str. 40
39099 Göttingen
--
Dept. of General Surgery
University of Göttingen
Göttingen, Germany
--
http://www.gwdg.de/~agoralc