External Validity in Fuzzy Regression Discontinuity Designs

30 Pages Posted: 22 Dec 2014

See all articles by Marinho Bertanha

Marinho Bertanha

University of Notre Dame - Department of Economics

Guido W. Imbens

Stanford Graduate School of Business

Date Written: December 2014

Abstract

Many empirical studies use Fuzzy Regression Discontinuity (FRD) designs to identify treatment effects when the receipt of treatment is potentially correlated to outcomes. Existing FRD methods identify the local average treatment effect (LATE) on the subpopulation of compliers with values of the forcing variable that are equal to the threshold. We develop methods that assess the plausibility of generalizing LATE to subpopulations other than compliers, and to subpopulations other than those with forcing variable equal to the threshold. Specifically, we focus on testing the equality of the distributions of potential outcomes for treated compliers and always-takers, and for non-treated compliers and never-takers. We show that equality of these pairs of distributions implies that the expected outcome conditional on the forcing variable and the treatment status is continuous in the forcing variable at the threshold, for each of the two treatment regimes. As a matter of routine, we recommend that researchers present graphs with estimates of these two conditional expectations in addition to graphs with estimates of the expected outcome conditional on the forcing variable alone. We illustrate our methods using data on the academic performance of students attending the summer school program in two large school districts in the US.

Suggested Citation

Bertanha, Marinho and Imbens, Guido W., External Validity in Fuzzy Regression Discontinuity Designs (December 2014). NBER Working Paper No. w20773. Available at SSRN: https://ssrn.com/abstract=2541549

Marinho Bertanha (Contact Author)

University of Notre Dame - Department of Economics ( email )

Notre Dame, IN 46556
United States

Guido W. Imbens

Stanford Graduate School of Business ( email )

655 Knight Way
Stanford, CA 94305-5015
United States

Register to save articles to
your library

Register

Paper statistics

Downloads
16
Abstract Views
178
PlumX Metrics