arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2004.14497math.STstat.TH
收藏

迈向异质性因果效应的最优双重稳健估计

Towards optimal doubly robust estimation of heterogeneous causal effects

Edward H. Kennedy

AI总结:

本文研究异质性 CATE 估计的最优性,提出两阶段双重稳健估计量、通用误差界与局部多项式双残差回归,给出 oracle 效率条件及非 oracle 情形误差界。

摘要:

异质性效应估计在因果推断中发挥着关键作用,并在医学和社会科学中有着广泛应用。近年来,人们提出了许多用于估计条件平均处理效应(CATE)的方法,但在理解这些方法是否以及何时达到最优方面,仍存在重要的理论空白。当 CATE 具有非平凡结构(例如平滑性或稀疏性)时,情况尤其如此。我们的工作主要在几个方面作出贡献。首先,我们研究了一种两阶段双重稳健 CATE 估计量,并给出了一个通用的、不依赖模型的误差界;尽管具有一般性,该误差界仍能产生比当前文献中更锐利的结果。我们应用该界来推导具有平滑性或稀疏性的非参数模型中的误差率,并给出 oracle 效率的充分条件。我们的误差界基于一个用于带有估计或插补结果的回归问题的通用 oracle 不等式,该不等式本身具有独立的研究价值;这是第二项主要贡献。第三项贡献旨在理解 CATE 估计的基本统计极限。为此,我们提出并研究了双残差回归的局部多项式适配版本。我们表明,如果结合一种特殊形式的样本划分以及对调谐参数的谨慎选择,该估计量即使在更弱的条件下也可以达到 oracle 效率。这些是目前文献中发现的最弱条件,并且我们猜想它们在 minimax 意义下是极小的。我们进一步给出了在无法达到 oracle 速率的非平凡情形下的误差界。最后,我们通过模拟探索了若干有限样本性质。

英文摘要:

Heterogeneous effect estimation plays a crucial role in causal inference, with applications across medicine and social science. Many methods for estimating conditional average treatment effects (CATEs) have been proposed in recent years, but there are important theoretical gaps in understanding if and when such methods are optimal. This is especially true when the CATE has nontrivial structure (e.g., smoothness or sparsity). Our work contributes in several main ways. First, we study a two-stage doubly robust CATE estimator and give a generic model-free error bound, which, despite its generality, yields sharper results than those in the current literature. We apply the bound to derive error rates in nonparametric models with smoothness or sparsity, and give sufficient conditions for oracle efficiency. Underlying our error bound is a general oracle inequality for regression with estimated or imputed outcomes, which is of independent interest; this is the second main contribution. The third contribution is aimed at understanding the fundamental statistical limits of CATE estimation. To that end, we propose and study a local polynomial adaptation of double-residual regression. We show that this estimator can be oracle efficient under even weaker conditions, if used with a specialized form of sample splitting and careful choices of tuning parameters. These are the weakest conditions currently found in the literature, and we conjecture that they are minimal in a minimax sense. We go on to give error bounds in the non-trivial regime where oracle rates cannot be achieved. Some finite-sample properties are explored with simulations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑