This study examines whether unobserved factors substantially bias education evaluations that rely on the Conditional Independence Assumption. We add 14 new within‐study comparisons to the literature, all from primary schools in England. Across these 14 studies, we generate 42 estimates of selection bias using a simple approach to observational analysis. A meta‐analysis of these estimates suggests that the distribution of underlying bias is centered around zero. The mean absolute value of estimated bias is 0.03σ, and none of the 42 estimates are larger than 0.11σ. Results are similar for math, reading, and writing outcomes. Overall, we find no evidence of substantial selection bias due to unobserved characteristics. These findings may not generalize easily to other settings or to more radical educational interventions, but they do suggest that non‐experimental approaches could play a greater role than they currently do in generating reliable causal evidence for school education.

中文翻译：

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吸引推理怪物？在学校课程评估中量化选择偏见

这项研究检查了未观察到的因素是否严重偏向依赖于条件独立假设的教育评估。我们在文献中添加了14种新的研究性内部比较，全部来自英格兰的小学。在这14项研究中，我们使用一种简单的观察分析方法生成了42个选择偏见的估计。对这些估计的荟萃分析表明，基本偏差的分布集中在零附近。估计偏差的平均绝对值为0.03σ，并且42个估计值均不大于0.11σ。数学，阅读和写作结果的结果相似。总体而言，我们没有发现由于未观察到的特征而导致实质性选择偏见的证据。这些发现可能无法轻易推广到其他环境或更激进的教育干预措施，