Date:         Sat, 16 Apr 2005 08:44:37 -0400
Reply-To:     "Boye, Mark" <mark.boye@PFIZER.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Boye, Mark" <mark.boye@PFIZER.COM>
Subject:      Estimators for 2-equation Random Effects Panel Data
Content-Type: text/plain; charset="iso-8859-1"

I am evaluating a clinical trial with 9 sequential days of data and am
attempting to model the following: dichotomous treatment group
assignment->variation in opioid consumption -> variation in patient-reported
opioid symptoms (e.g., drowsiness, nausea, difficulty with urination, etc).
The dependent patient-reported variables are dichotomous (symptom yes/no),
count (how many daily episodes), and continuous(patient-rated symptom
severity 0-4).

Including group assignment and opioid consumption on the RHS of a single
equation would possibly introduce endogeneity issues and would also fail to
completely model this causal sequence; I therefore envision a 2-equation
solution first regressing the continuous variable opioid consumption onto
group assignment.  Thereafter the second equation would incorporate the
residual to estimate the effect on my various patient-reported outcome
measures (e.g., 0/1, count, and continuous measures).

Research questions I am attempting to answer include the treatment effect on
both opioid consumption and opioid symptoms, and the dose-response effect of
opioid consumption on opioid-related symptoms.

Are there 2-equation random effect panel estimators available in SAS to fit
such models to these data?  If not, are you aware of any other routines in
other software that I could use to conduct these analyses.


Thank you,
Mark Boye



Mark E. Boye MBA, MPH, Ph.D.
Senior Outcomes Research Scientist
WW Outcomes Research
2800 Plymouth Road
Ann Arbor, MI  48105
Tel 734-622-4856
E-mail mark.boye@pfizer.com


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