Personalized Incentive Alignment: Correcting Utility-Driven Selection Bias in A/B Tests

Although A/B testing is a powerful tool for estimating the average treatment effect (ATE), it often proves impractical in social or commercial settings because ethical and business constraints induce participant non-compliance. For example, patients may refuse assignment to less promising therapies, and users may choose whether to adopt a newly released feature based on personal preferences. In this work, we posit that participants act to maximize individual incentives. To capture this behavior, we adopt a utility-based random choice model that explicitly characterizes the identification bias introduced by self-selection and the estimation instability caused by feature imbalance. We then demonstrate how heterogeneous incentives generate both selection bias and inflated variance. Building on these insights, we design an optimal incentive mechanism that equalizes preference distributions across treatment arms, thereby achieving a more balanced covariate profile, lower variance, and a sharper identified set with minimal bias. Finally, we propose an online learning framework that adaptively identifies the optimal incentive scheme during the experiment and produces valid treatment-effect estimates. We validate our theoretical results through both simulation studies and field experiments.