The Regression Discontinuity (RD) design is a widely used non-experimental method for causal inference and program evaluation. While its canonical formulation only requires a score and an outcome variable, it is common in empirical work to encounter RD implementations where additional variables are used for adjustment. This practice has led to misconceptions about the role of covariate adjustment in RD analysis, from both methodological and empirical perspectives. In this chapter, we review the different roles of covariate adjustment in RD designs, and offer methodological guidance for its correct use in applications.

翻译：递减中断设计是广泛使用的因果推断和方案评价的非实验性方法。虽然其精度配方只需要一个分数和一个结果变量,但在实证工作中常见的情况是,在运用其他变数进行调整的情况下遇到RD执行过程。从方法和经验角度来看,这种做法导致了对RD分析中共变调整作用的误解。本章我们审查了RD设计中共变调整的不同作用,并为应用中正确使用它提供了方法指导。