I started the following at
http://groups.google.com/group/sci.stat.consult/browse_frm/thread/ac64f6191ec7809b/4ab3bfb11c7f08cd?hl=sl#4ab3bfb11c7f08cd
and perhaps someone here can help me.
Hello!
I am analysing data on behaviour of animals. I have a factor at 1-level
i.e. fixed effect and I also added animal indicator as 2-level i.e.
random effect of my model, as there is considerable variation between
animals. Very often one assumes that 2-level units are independent, but
in my case this might not be the case, since animals within one level
of a factor were in contact and might influence on each other.
I could model this dependency as say multivariate normal with
particular covariance matrix for 2-level within each factor, but I have
not came accros any such examples. I a bit skeptic in amount of
information to estimate "many" covariance components. For now compound
symmetry, unstructured and Toeplitz (in SAS parlance[1]) structures for
covariance matrix have come to my mind fot this task.
Does anyone have any experience in this type of models? Any
suggestions, comments, pointer to relevant literature are more than
welcome.
Thanks!
[1]http://v8doc.sas.com/sashtml/stat/chap41/sect20.htm#mixedspcovstruct
--
Lep pozdrav / With regards,
Gregor Gorjanc
