Linden Consulting Group, Ann Arbor, MI 48103, USA.
J Eval Clin Pract. 2012 Apr;18(2):317-25. doi: 10.1111/j.1365-2753.2011.01768.x. Epub 2012 Feb 5.
The regression discontinuity (RD) design is considered to be the closest to a randomized trial that can be applied in non-experimental settings. The design relies on a cut-off point on a continuous baseline variable to assign individuals to treatment. The individuals just to the right and left of the cut-off are assumed to be exchangeable - as in a randomized trial. Any observed discontinuity in the relationship between the assignment variable and outcome is therefore considered evidence of a treatment effect. In this paper, we describe key advances in the RD design over the past decade and illustrate their implementation using data from a health management intervention. We then introduce the propensity score-based weighting technique as a complement to the RD design to correct for imbalances in baseline characteristics between treated and non-treated groups that may bias RD results. We find that the weighting strategy outperforms standard regression covariate adjustment in the present data. One clear advantage of the weighting technique over regression covariate adjustment is that we can directly inspect the degree to which balance was achieved. Because of its relative simplicity and tremendous utility, the RD design (either alone or combined with propensity score weighting adjustment) should be considered as an alternative approach to evaluate health management program effectiveness when using observational data.
回归间断设计（RD 设计）被认为是最接近随机试验的非实验设置方法。该设计依赖于连续基线变量上的一个截断点来将个体分配到治疗组。截断点左右两侧的个体被认为是可交换的——就像在随机试验中一样。因此，分配变量与结果之间任何观察到的不连续性都被认为是治疗效果的证据。在本文中，我们描述了过去十年中 RD 设计的关键进展，并使用健康管理干预的数据说明了其实施情况。然后，我们引入基于倾向评分的加权技术作为 RD 设计的补充，以纠正治疗组和未治疗组之间基线特征的不平衡，这些不平衡可能会使 RD 结果产生偏差。我们发现，在本数据中，加权策略优于标准回归协变量调整。与回归协变量调整相比，加权技术的一个明显优势是，我们可以直接检查实现平衡的程度。由于其相对简单性和巨大的实用性，当使用观察数据评估健康管理计划的效果时，RD 设计（单独使用或与倾向评分加权调整结合使用）都应被视为一种替代方法。
