丁鹏,加州大学伯克利分校统计系副教授。2015年5月在哈佛大学统计系获得博士学位,随后在哈佛大学陈曾熙公共卫生学院(Harvard T. H. Chan School of Public Health)流行病学系从事博士后研究工作,直至2015年12月。此前,他在北京大学获得数学学士、经济学学士以及统计学硕士学位。
Identification and multiply robust estimation of causal effects via instrumental variables from an auxiliary population
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论文摘要
Estimating causal effects in a target population with unmeasured confounders is challenging, especially when instrumental variables (IVs) are unavailable. However, IVs from auxiliary populations with similar problems can help infer causal effects in the target population. While the homogeneous conditional average treatment effect assumption has been widely used for effect transportability, it has not been explored in IV-based data fusion. We include it as a basic approach, though it may be biased when treatment effect heterogeneity exists. As an alternative approach, we introduce the equi-confounding assumption that the unmeasured confounding bias remains the same after adjusting for observed covariates, while allowing conditional average treatment effects to differ across populations. This allows us to identify the confounding bias in the auxiliary population and remove it from the treatment-outcome association in the target population to recover the causal effect. We develop multiply robust estimators under both approaches and demonstrate them through simulation studies and a real data application.