Asymdystopia: The Threat of Small Biases in Evaluations of Education Interventions (Working Paper)

Abstract

Evaluators of education interventions are increasingly designing studies to detect impacts much smaller than the 0.20 standard deviations that Cohen (1988) characterized as “small.” While the need to detect smaller impacts is based on compelling arguments that such impacts are substantively meaningful, the drive to detect smaller impacts may create a new challenge for researchers: the need to guard against smaller biases. The purpose of this paper is twofold. First, we examine the potential for small biases to increase the risk of making false inferences as studies are powered to detect smaller impacts, a phenomenon we refer to as asymdystopia. We examine this potential for two of the most rigorous designs commonly used in education research—randomized controlled trials (RCTs) and regression discontinuity designs (RDDs). Second, we recommend strategies researchers can use to avoid or mitigate these biases.