[gov3009-l] Gov 3009 April 23: Stuart

Elizabeth Stuart stuart@stat.harvard.edu
Sun, 20 Apr 2003 14:47:27 -0400 (EDT)

This week's speaker at the Gov 3009 workshop is Elizabeth Stuart from the
Department of Statistics.  She will be speaking on 
"Matching and the Use of Multiple Control Groups in the Context of Causal 

In observational studies, it is desirable to reduce bias due to
covariates by obtaining treated and control groups with similar
distributions of the covariates. This is often done by choosing well
matched samples of the original treated and control groups. However,
sometimes the originally chosen control units cannot provide adequate
matches for the treated units. In these cases, it may be desirable to
obtain matched controls from two control groups. Multiple control groups
have been used in the context of causal inference to test for hidden
biases; however, little work has been done on their use in matching or
adjustment for these biases. In this talk, we address two issues
associated with the use of multiple control groups. The first relates to
longitudinal data and the necessity to define ``baseline" for
non-randomized control units. This will be discussed in the context of a
randomized clinical trial for a drug that may become commercially
available, thus invalidating the traditional use of the control group.
Historical data on patients with the disease will be used to supplement
the original randomized control group. The second issue discussed will be
how to quantify differences in unobserved variables between multiple
control groups. Quantifying this bias can help guide the use of multiple
control groups. This topic will be discussed in the context of the
evaluation of a school-wide dropout prevention program where students in
the original treated and control schools were significantly different from
one another. The method explores the use of external national data on high
school students in addition to the local control students. 

This is work in progress; no paper is available. 

Seminar Information:
The seminar meets at noon in Room 22, Center for Basic Research
in Social Sciences (CBRSS, 34 Kirkland St., this is the yellow building
across the street from William James Hall). Contact information, previous
presentations, and the spring schedule may be found at the course web
site: http://www.courses.fas.harvard.edu/~gov3009/.  Lunch is provided.

To join the gov3009 mailing list, send e-mail to
gov3009-l-request@fas.harvard.edu with the following text message:


Questions?  Please contact the workshop coordinator, Liz Stuart, at