Measuring the effect of peers on individuals' outcomes is a challenging problem, in part because individuals often select peers who are similar in both observable and unobservable ways. Group formation experiments avoid this problem by randomly assigning individuals to groups and observing their responses; for example, do first-year students have better grades when they are randomly assigned roommates who have stronger academic backgrounds? In this paper, we propose randomization-based permutation tests for group formation experiments, extending classical Fisher Randomization Tests to this setting. The proposed tests are justified by the randomization itself, require relatively few assumptions, and are exact in finite-samples. This approach can also complement existing strategies, such as linear-in-means models, by using a regression coefficient as the test statistic. We apply the proposed tests to two recent group formation experiments.

翻译：衡量同伴对个体结果的影响是一个具有挑战性的问题，部分原因在于个体往往会选择在可观测和不可观测特征上与自己相似的同伴。群组形成实验通过将个体随机分配至群组并观测其反应来避免这一问题；例如，当新生被随机分配至学业背景更强的室友时，他们的成绩是否会更优异？本文针对群组形成实验提出了基于随机化的置换检验方法，将经典Fisher随机化检验扩展至该场景。所提出的检验方法以随机化本身为理论基础，所需假设较少，且在有限样本条件下具有精确性。该方法还能通过将回归系数作为检验统计量，对现有策略（如线性均值模型）进行补充。我们将所提出的检验方法应用于两个近期的群组形成实验。