On Efficient Estimation of Distributional Treatment Effects under Covariate-Adaptive Randomization

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Main Authors: Byambadalai, Undral, Hirata, Tomu, Oka, Tatsushi, Yasui, Shota
Format: Preprint
Published: 2025
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author Byambadalai, Undral
Hirata, Tomu
Oka, Tatsushi
Yasui, Shota
author_facet Byambadalai, Undral
Hirata, Tomu
Oka, Tatsushi
Yasui, Shota
contents This paper focuses on the estimation of distributional treatment effects in randomized experiments that use covariate-adaptive randomization (CAR). These include designs such as Efron's biased-coin design and stratified block randomization, where participants are first grouped into strata based on baseline covariates and assigned treatments within each stratum to ensure balance across groups. In practice, datasets often contain additional covariates beyond the strata indicators. We propose a flexible distribution regression framework that leverages off-the-shelf machine learning methods to incorporate these additional covariates, enhancing the precision of distributional treatment effect estimates. We establish the asymptotic distribution of the proposed estimator and introduce a valid inference procedure. Furthermore, we derive the semiparametric efficiency bound for distributional treatment effects under CAR and demonstrate that our regression-adjusted estimator attains this bound. Simulation studies and empirical analyses of microcredit programs highlight the practical advantages of our method.
format Preprint
id arxiv_https___arxiv_org_abs_2506_05945
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On Efficient Estimation of Distributional Treatment Effects under Covariate-Adaptive Randomization
Byambadalai, Undral
Hirata, Tomu
Oka, Tatsushi
Yasui, Shota
Econometrics
Statistics Theory
Machine Learning
This paper focuses on the estimation of distributional treatment effects in randomized experiments that use covariate-adaptive randomization (CAR). These include designs such as Efron's biased-coin design and stratified block randomization, where participants are first grouped into strata based on baseline covariates and assigned treatments within each stratum to ensure balance across groups. In practice, datasets often contain additional covariates beyond the strata indicators. We propose a flexible distribution regression framework that leverages off-the-shelf machine learning methods to incorporate these additional covariates, enhancing the precision of distributional treatment effect estimates. We establish the asymptotic distribution of the proposed estimator and introduce a valid inference procedure. Furthermore, we derive the semiparametric efficiency bound for distributional treatment effects under CAR and demonstrate that our regression-adjusted estimator attains this bound. Simulation studies and empirical analyses of microcredit programs highlight the practical advantages of our method.
title On Efficient Estimation of Distributional Treatment Effects under Covariate-Adaptive Randomization
topic Econometrics
Statistics Theory
Machine Learning
url https://arxiv.org/abs/2506.05945