What Is One of the Limitations of Using RD Models

Multiple Choice

What is one of the limitations of using RD models in order to help make/shape policy decisions?

A) The treatment effect may not be generalizable.
B) The cost of running and setting up an experiment to run an RD model can be prohibitively expensive.
C) Different assignment variables (and corresponding cutoff) can show treatment effects, difficult to tell which assignment variable is accurate.
D) Policymakers are much more comfortable randomly assigning treatment status than assigning treatment based on some assignment variable such as a test score or needs index.