Regression discontinuity analysis is a statistical tool that allows researchers to examine the effectiveness of the treatment in such studies. Consider the following: One researcher wants to determine whether tutoring underachieving middle school students improves their math grades; another wonders whether providing financial aid to [Page 1388]low-income students has the desired effects on student success and dropout rates; and a third hopes to assess the effectiveness of special support programs for promising high school athletes. These studies fit the definition of a regression discontinuity design, whereby participants who satisfy a chosen criterion are assigned to a certain treatment and some outcome variable is measured later.

Regression discontinuity analysis is used for studies in which participants are assigned to treatment conditions based on a known assignment rule ...