Random Measurement Error Does Not Bias the Treatment Effect Estimate in the Regression-Discontinuity Design

Abstract

A recently published Evaluation Review article (April 1990) claimed that because of random measurement error in the pretest (and the regression toward the mean that results) the estimate of the treatment effect of the regression-discontinuity (RD) design is biased A conceptual approach and a set of computer simulations are presented to arrive at the opposite conclusion: random measurement error in the pretest does not bias the estimate of the treatment effect in the RD design. This article, the first of two dealing with measurement error in the RD design, concentrates specifically on the case of no interaction between pretest and treatment on posttest. The claim that the RD effect estimate is not biased due to measurement error is in full agreement with the conclusion reached by several authors who have examined the design over the last two decades.