协变量
混淆
观察研究
估计员
统计
计量经济学
灵敏度(控制系统)
稳健性(进化)
非参数统计
倾向得分匹配
数学
计算机科学
工程类
生物化学
基因
电子工程
化学
作者
Matteo Bonvini,Edward H. Kennedy
标识
DOI:10.1080/01621459.2020.1864382
摘要
In observational studies, identification of ATEs is generally achieved by assuming that the correct set of confounders has been measured and properly included in the relevant models. Because this assumption is both strong and untestable, a sensitivity analysis should be performed. Common approaches include modeling the bias directly or varying the propensity scores to probe the effects of a potential unmeasured confounder. In this article, we take a novel approach whereby the sensitivity parameter is the "proportion of unmeasured confounding": the proportion of units for whom the treatment is not as good as randomized even after conditioning on the observed covariates. We consider different assumptions on the probability of a unit being unconfounded. In each case, we derive sharp bounds on the average treatment effect as a function of the sensitivity parameter and propose nonparametric estimators that allow flexible covariate adjustment. We also introduce a one-number summary of a study's robustness to the number of confounded units. Finally, we explore finite-sample properties via simulation, and apply the methods to an observational database used to assess the effects of right heart catheterization. Supplementary materials for this article are available online.
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