The Power of Optimization Over Randomization in Designing Experiments Involving Small Samples

Random assignment, typically seen as the standard in controlled trials, aims to make experimental groups statistically equivalent before treatment. However, with a small sample, which is a practical reality in many disciplines, randomized groups are often too dissimilar to be useful. We propose an a...

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Bibliographic Details
Main Authors: Johnson, Mac, Kallus, Nathan, Bertsimas, Dimitris J
Other Authors: Massachusetts Institute of Technology. Operations Research Center
Format: Article
Language:en_US
Published: Institute for Operations Research and the Management Sciences (INFORMS) 2015
Online Access:http://hdl.handle.net/1721.1/98509
https://orcid.org/0000-0003-1672-0507
https://orcid.org/0000-0002-1985-1003
Description
Summary:Random assignment, typically seen as the standard in controlled trials, aims to make experimental groups statistically equivalent before treatment. However, with a small sample, which is a practical reality in many disciplines, randomized groups are often too dissimilar to be useful. We propose an approach based on discrete linear optimization to create groups whose discrepancy in their means and variances is several orders of magnitude smaller than with randomization. We provide theoretical and computational evidence that groups created by optimization have exponentially lower discrepancy than those created by randomization and that this allows for more powerful statistical inference.