Falsification Tests for Instrumental Variable Designs With an Application to Tendency to Operate
Falsification Tests for Instrumental Variable Designs With an Application to Tendency to Operate
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DOI：
10.1097/mlr.0000000000001040
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发表时间：
2019-02-01
期刊：
影响因子：
3
通讯作者：
Small, Dylan
中科院分区：
文献类型：
--
作者：
Keele, Luke;Zhao, Qingyuan;Small, Dylan
背景：工具变量(IV)方法正在成为卫生服务研究中越来越重要的工具，因为它们可以在存在未观察到的混淆的情况下提供对因果影响的一致估计。然而，调查人员必须提供理由，证明静脉注射与任何未测量的混杂因素无关，而且它对结果的影响只有通过接受接触才能发生。这些假设虽然在某些情况下看似合理，但无法从数据中得到验证。方法：可以应用证伪测试来为关键的IV假设提供证据。证伪测试不能证明假设成立，但可以在假设失败时提供决定性证据。我们提供了IV设计的证伪测试的一般概述。我们重点介绍了一个证伪测试，该测试利用了数据中的一个子总体，其中绝大多数单元被处理或未处理。如果IV假设成立，我们应该发现意向治疗效应在这些亚群中为零。结果：我们演示了使用来自卫生服务研究的被称为操作倾向的IV的IV设计的证伪测试的使用。我们表明，证伪测试没有提供任何证据来反对本申请中的IV假设。
Background: Instrumental variable (IV) methods are becoming an increasingly important tool in health services research as they can provide consistent estimates of causal effects in the presence of unobserved confounding. However, investigators must provide justifications that the IV is independent with any unmeasured confounder and its effect on the outcome occurs only through receipt of the exposure. These assumptions, while plausible in some contexts, cannot be verified from the data. Methods: Falsification tests can be applied to provide evidence for the key IV assumptions. A falsification test cannot prove the assumptions hold, but can provide decisive evidence when the assumption fails. We provide a general overview of falsification tests for IV designs. We highlight a falsification test that utilizes a subpopulation of the data where an overwhelming proportion of units are treated or untreated. If the IV assumptions hold, we should find the intention-to-treat effect is zero within these subpopulations. Results: We demonstrate the usage of falsification tests for IV designs using an IV known as tendency to operate from health services research. We show that the falsification test provides no evidence against the IV assumptions in this application.