Regression discontinuity (RD) designs are a popular approach to estimating a treatment effect of cutoff-based interventions. Two current estimation approaches dominate the literature. One fits separate regressions on either side of the cutoff, and the other performs finite sample inference based on a local randomization assumption. Recent developments of these approaches have often focused on asymptotic properties and large sample sizes. Educational applications often contain relatively small samples or sparsity near the cutoff, making estimation more difficult. As an alternative to the aforementioned approaches, we develop a partial linear estimator for RD designs. We show in simulations that our estimator outperforms certain leading estimators in several realistic, small-sample scenarios. We apply our estimator to school accountability scores in Indiana.
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