Improved Policy Evaluation for Randomized Trials of Algorithmic Resource Allocation
This addresses a methodological challenge in RCTs for resource allocation, offering a more accurate evaluation tool for researchers and practitioners, though it is incremental in improving existing estimation methods.
The paper tackles the problem of evaluating algorithmic resource allocation policies in randomized controlled trials (RCTs) where outcomes are interlinked due to resource constraints, and presents a new estimator using retrospective reshuffling of participants to construct counterfactual trials, proving it is unbiased and reduces variance, with empirical demonstrations showing improved accuracy.
We consider the task of evaluating policies of algorithmic resource allocation through randomized controlled trials (RCTs). Such policies are tasked with optimizing the utilization of limited intervention resources, with the goal of maximizing the benefits derived. Evaluation of such allocation policies through RCTs proves difficult, notwithstanding the scale of the trial, because the individuals' outcomes are inextricably interlinked through resource constraints controlling the policy decisions. Our key contribution is to present a new estimator leveraging our proposed novel concept, that involves retrospective reshuffling of participants across experimental arms at the end of an RCT. We identify conditions under which such reassignments are permissible and can be leveraged to construct counterfactual trials, whose outcomes can be accurately ascertained, for free. We prove theoretically that such an estimator is more accurate than common estimators based on sample means -- we show that it returns an unbiased estimate and simultaneously reduces variance. We demonstrate the value of our approach through empirical experiments on synthetic, semi-synthetic as well as real case study data and show improved estimation accuracy across the board.