Date:         Fri, 5 Aug 2005 15:29:59 -0700
Reply-To:     ysli@MDANDERSON.ORG
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         ysli@MDANDERSON.ORG
Organization: http://groups.google.com
Subject:      help on random / repeated statements in SAS PROC MIXED
Comments: To: sas-l@uga.edu
Content-Type: text/plain; charset="iso-8859-1"

Dear all,

I have a question in specifying correct correlation structure using
random and/or repeated statements in SAS PROC MIXED when analyzing my
data.

The data set consists of multiple measurements during each day on
multiple days (1-21) for each of some number of subjects.  I'd like to
assume a random intercept due to subject, and a time series with
respect to day (so that measurements during a day share the same random
day effect) with an AR(1) correlation structure among observations on
different days.  I'm not concerned about whether to use random or
repeated statements as long as the correct correlation matrix is
specified.  Any hints or thoughts will be greatly appreciated.

Yisheng Li
MD Anderson Cancer Center
Houston, TX 77030