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An Improved Minimization Method: Eliminating Shift and Variance Inflation While Maintaining Marginal Balance
Abstract
Pocock and Simon's minimization method is a widely used approach for covariate-adaptive randomization in clinical trials. However, it can exhibit the shift problem under unequal allocation and variance inflation of the imbalances in additional covariates. In this paper, we propose a new minimization method that preserves the conventional biased-coin allocation probability while ensuring marginal imbalances bounded in probability. Meanwhile, the proposed procedure guarantees that neither the shift problem nor variance inflation occurs. Simulation and empirical studies demonstrate the excellent performance of the proposed procedure.
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BibTeX
@misc{tao2026improved,
title = {{An Improved Minimization Method: Eliminating Shift and Variance Inflation While Maintaining Marginal Balance}},
author = {Yuhang Tao and Li-Xin Zhang},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.08378},
eprint = {2611.08378},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.08378},
}
RIS
TY - UNPB
TI - An Improved Minimization Method: Eliminating Shift and Variance Inflation While Maintaining Marginal Balance
AU - Yuhang Tao
AU - Li-Xin Zhang
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2611.08378
UR - https://arxiv.org/abs/2611.08378
AB - Pocock and Simon's minimization method is a widely used approach for covariate-adaptive randomization in clinical trials. However, it can exhibit the shift problem under unequal allocation and variance inflation of the imbalances in additional covariates. In this paper, we propose a new minimization method that preserves the conventional biased-coin allocation probability while ensuring marginal imbalances bounded in probability. Meanwhile, the proposed procedure guarantees that neither the shift problem nor variance inflation occurs. Simulation and empirical studies demonstrate the excellent performance of the proposed procedure.
ER -