EFFICIENT RANDOMIZED-ADAPTIVE DESIGNS

• 成果类型: Article
• 署名作者: Hu, Feifang; Zhang, Li-Xin; He, Xuming
• 署名单位: University of Virginia; Zhejiang University; University of Illinois System; University of Illinois Urbana-Champaign
• 刊物名称: ANNALS OF STATISTICS
• ISSN/ISSBN: 0090-5364
• DOI: 10.1214/08-AOS655
• 发表日期: 2009
• 页码: 2543-2560
• 关键词: biased coin designs; sequential clinical-trials; play-winner rule; asymptotic properties; prognostic factors; urn models; variability; allocation

摘要

Response-adaptive randomization hits recently attracted a lot of attention in the literature. In this paper, we propose a new and simple family of response-adaptive randomization procedures that attain the cramer-Rao lower bounds on the allocation variances for any allocation proportions including optimal allocation proportions. The allocation Probability functions of proposed procedures are discontinuous. The existing large sample theory for adaptive designs relies on Taylor expansions of the allocation probability functions. which do not apply to nondifferentiable cases. In the present paper, we Study stopping times of stochastic processes to establish the asymptotic efficiency results. Furthermore, we demonstrate our proposal through examples, simulations and a discussion on the relationship with earlier works, including Efron's biased coin design.