Adaptive Experimental Design for Policy Learning

• URL: http://arxiv.org/abs/2401.03756v4
• Date: Thu, 19 Jun 2025 14:27:47 GMT
• Title: Adaptive Experimental Design for Policy Learning
• Authors: Masahiro Kato, Kyohei Okumura, Takuya Ishihara, Toru Kitagawa,
• Abstract summary: We consider a decision-maker who assigns treatment arms to experimental units during an experiment and recommends the estimated best treatment arm based on the contexts at the end of the experiment.<n>We focus on the worst-case expected regret, a measure between the expected outcomes of an optimal policy and our proposed policy.<n>We prove that this strategy is minimax rate-optimal in the sense that its leading factor in the regret upper bound matches the lower bound as the number of experimental units increases.
• Score: 8.73717644648873
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: This study investigates the contextual best arm identification (BAI) problem, aiming to design an adaptive experiment to identify the best treatment arm conditioned on contextual information (covariates). We consider a decision-maker who assigns treatment arms to experimental units during an experiment and recommends the estimated best treatment arm based on the contexts at the end of the experiment. The decision-maker uses a policy for recommendations, which is a function that provides the estimated best treatment arm given the contexts. In our evaluation, we focus on the worst-case expected regret, a relative measure between the expected outcomes of an optimal policy and our proposed policy. We derive a lower bound for the expected simple regret and then propose a strategy called Adaptive Sampling-Policy Learning (PLAS). We prove that this strategy is minimax rate-optimal in the sense that its leading factor in the regret upper bound matches the lower bound as the number of experimental units increases.

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