Regression Discontinuity - Institute for Policy Research

3. Semi-Parametric Approach
Y
i
= t D + f ( Z ) + X ã + e
i
• Where Y i , D i , and X i are the same as before, and f(Z i ) in the
generalized additive model is the smooth function of the
assignment variable for the control and treatment groups.
• The smooth function is typically modeled using a series of
splines.
• Treatment effect ( ) may be estimated via thin plate regression
splines using the mcgv-package in R (R Development Core
Team, 2009; Wood, 2006).
• Advantage is that it allows for flexibility in modeling the
response function while controlling for baseline covariates in
the model.
i
t
i
i