arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.09676stat.MEecon.EM
收藏

在观察性研究中使用实验来纠正选择偏差

Using Experiments to Correct for Selection in Observational Studies

Susan Athey, Raj Chetty, Guido Imbens

AI总结:

针对观察性数据存在选择偏差而实验数据缺乏主要结果的问题,提出基于潜在无混杂假设的选择偏差纠正方法,利用次要结果预测差异估计处理效应,实验证明其能有效消除偏差并复现实验结果。

摘要:

研究人员越来越多地获得两类数据:(i)大型观察性数据集,其中处理(如班级规模)未随机化,但观察到了几个主要结果(如毕业率)和次要结果(如考试分数);(ii)实验数据,其中处理是随机化的,但仅观察到次要结果。我们开发了一种新方法来估计此类环境中对主要结果的处理效应。我们使用次要结果与其基于实验处理效应的预测值之间的差异,来衡量观察性数据中的选择偏差。在一种我们称之为“潜在无混杂”的新假设下,控制这种选择偏差的估计值,可以产生对主要结果处理效应的无偏估计。该假设要求相同的混杂因素影响主要和次要结果。潜在无混杂弱化了常用替代估计量的假设。我们应用我们的估计量来识别三年级班级规模对学生结果的影响。在观察性学区数据中,使用OLS回归对考试分数的估计影响与Tennessee STAR实验的估计符号相反。相比之下,观察性数据中经过选择偏差纠正的估计值重现了实验估计值。我们的估计量表明,班级规模减少25%会使高中毕业率提高0.7个百分点。控制可观测变量并不能改变OLS估计值,这表明实验性选择纠正可以消除标准控制方法无法解决的偏差。

英文摘要:

Researchers increasingly have access to two types of data: (i) large observational datasets where treatment (e.g., class size) is not randomized but several primary outcomes (e.g., graduation rates) and secondary outcomes (e.g., test scores) are observed and (ii) experimental data in which treatment is randomized but only secondary outcomes are observed. We develop a new method to estimate treatment effects on primary outcomes in such settings. We use the difference between the secondary outcome and its predicted value based on the experimental treatment effect to measure selection bias in the observational data. Controlling for this estimate of selection bias yields an unbiased estimate of the treatment effect on the primary outcome under a new assumption that we term latent unconfoundedness, which requires that the same confounders affect the primary and secondary outcomes. Latent unconfoundedness weakens the assumptions underlying commonly used surrogate estimators. We apply our estimator to identify the effect of third grade class size on students outcomes. Estimated impacts on test scores using OLS regressions in observational school district data have the opposite sign of estimates from the Tennessee STAR experiment. In contrast, selection-corrected estimates in the observational data replicate the experimental estimates. Our estimator reveals that reducing class sizes by 25% increases high school graduation rates by 0.7 percentage points. Controlling for observables does not change the OLS estimates, demonstrating that experimental selection correction can remove biases that cannot be addressed with standard controls.

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。

↑