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arXiv · 0803.3757

On regression adjustments in experiments with several treatments

David A. Freedman
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Abstract

Regression adjustments are often made to experimental data. Since randomization does not justify the models, bias is likely; nor are the usual variance calculations to be trusted. Here, we evaluate regression adjustments using Neyman's nonparametric model. Previous results are generalized, and more intuitive proofs are given. A bias term is isolated, and conditions are given for unbiased estimation in finite samples.

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David A. Freedman. 2008-03-26. On regression adjustments in experiments with several treatments. https://doi.org/10.1214/07-aoas143

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