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Author List:
Glickman ME
Workshop Objectives:
Least-squares regression and logistic regression
are among the most common statistical tools applied to health services
data to assess relationships between predictor variables and a
dependent variable. However, blind use of these regression techniques
can result in misleading conclusions. For example,
if some predictor variables are not transformed appropriately, they
may be determined to be not statistically significant when they are
important variables. Furthermore, potential predictors may be important in
a regression only when interacted with other variables, and such interactions
are often difficult to know a priori. The use of
classification and regression trees (CART) as an exploratory tool, or
even as an alternative to conventional regression techniques,
addresses some of these difficulties. CART, developed by
Breiman et al. (1984), is a flexible method based on recursive
partitioning of the data to model a continuous or categorical dependent
variable from a set of predictors. CART is becoming a more accepted tool
in health services applications, so it is worthwhile for
researchers to be aware of its use, as well as its benefits
and limitations compared to conventional regression techniques.
The objectives of this workshop are for
participants to (1) learn the fundamentals of CART, (2) be able to
interpret the results of CART applied to health services
regression data, and (3) understand the relationship between CART and
conventional regression methods, and how CART can help to guide modeling
choices in standard regression.
Activities:
After explaining the general principles of CART, and highlighting them
through simple examples, the application of CART will be demonstrated
on several health services data sets. Applications will be presented from
the output of S-Plus statistical software. Audience participants will
be provided handouts that both summarize workshop material and contain
short self-test exercises.
Target Audience:
The workshop is intended for health service researchers who use regression
methods in their work.
Assumed Audience Familiarity with Topic:
Workshop participants should have basic familiarity with regression at the
level of an introductory statistics course. No prior knowledge of CART is
assumed.
