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st: Discrete choice estimation
From
"Data Analytics Corp." <[email protected]>
To
Stata Listserve <[email protected]>
Subject
st: Discrete choice estimation
Date
Fri, 14 May 2010 10:52:22 -0400
Hi Stata,
I want to estimate a stated preference discrete choice model in Stata
(Stata 11 on Windows). Let's say it's just a simple binary model with
alternatives A and B. For a forced choice problem, I don't have a
problem doing the estimation. I would use clogit with group(caseID)
where caseID specifies each alternative for each choice set for each
person. My problem is that a Neither is included. The original design
matrix only has the two alternatives for the forced choice. The Neither
was added in the questionnaire as it should be. Suppose my data consist
of three independent variables (Color, Shape, Price), all categorical.
It seems that the data for the first two choice sets, therefore, should be
RespondentID Set caseid choice Color
Shape Price
1 1 1 0
red square low
1 1 1 1
blue round high
1 1 1 0
none none none
1 2 2 0
blue round high
1 2 2 0
blue round low
1 2 2 1
none none none
where the third and sixth rows reflects the Neither. Only rows 1,2,4,5
are from the design matrix where rows 1 and 2 are for alternative A and
the second for B; similarly for 4 and 5. The last is added afterward to
reflect Neither. Is this correct? The Stata command would be
xi: clogit choice i.Color i.Shape i.Price, group(caseID)
How does Stata handle the estimation? Is the Neither alternative
omitted (I suspect so)? If so, is the effect of Neither 0?
Thanks,
Walt
________________________
Walter R. Paczkowski, Ph.D.
Data Analytics Corp.
44 Hamilton Lane
Plainsboro, NJ 08536
________________________
(V) 609-936-8999
(F) 609-936-3733
[email protected]
www.dataanalyticscorp.com
_____________________________________________________
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