nested random effects

On Wed, 2005-03-23 at 11:58 -0500, Shaw, Philip (NIH/NIMH) wrote:

Hi
 
I am struggling with nested random effects and hope someone 

can help.

 


I have individuals (ID) who are nested within families 

(FAM).  I want to

model an outcome variable, and take account of the 

intercorrelation of

individuals within each family. 
 
I think this amounts to two random effects, one nested 

within the other.

 
How can I model this in R?
 
So far I have tried using the library(nlme), and then
 
Y~ID, random=~1|ID*FAM, 
 

An interaction random effect/fixed effect is noted as 

random ~1|random/fixed

in your case random =~1|ID/FAM (but I don't uderstand why indiviuals
withing families are fixed and and families are random, but there you
go).

Check out Pinheiro and Bates Ch1, especially pg 23 onwards.

Cheers,

F 
-- 
Federico C. F. Calboli
Department of Epidemiology and Public Health
Imperial College, St Mary's Campus
Norfolk Place, London W2 1PG

Tel  +44 (0)20 7594 1602     Fax (+44) 020 7594 3193

f.calboli [.a.t] imperial.ac.uk
f.calboli [.a.t] gmail.com