To adjust or not to adjust? Estimating the average treatment effect in randomized experiments with missing covariates
调整还是不调整:协变量缺失的随机实验中平均处理效应估计
Complete randomization allows for consistent estimation of the average treatment effect based on the difference in means of the outcomes without strong modeling assumptions on the outcome-generating process. Appropriate use of the pretreatment covariates can further improve the estimation efficiency. However, missingness in covariates is common in experiments and raises an important question: should we adjust for covariates subject to missingness, and if so, how? The…