Clarifying Selection Bias in Cluster Randomized Trials: Estimands and Estimation
厘清整群随机试验的选择偏差:目标参数与估计
In cluster randomized trials, patients are typically recruited after clusters are randomized, and the recruiters and patients may not be blinded to the assignment. This often leads to differential recruitment and consequently systematic differences in baseline characteristics of the recruited patients between intervention and control arms, inducing post-randomization selection bias. We rigorously define causal estimands in the presence of selection bias. We elucidate the…