A play-the-winner-type urn design with reduced variability

We propose a new adaptive allocation rule, the drop-the-loser, that randomizes subjects in the course of a trial comparing treatments with dichotomous outcomes. The rule tends to assign more patients to better treatments with the same limiting proportion as the randomized play-the-winner rule. The new design has significantly less variable allocation proportion than the randomized play-the-winner rule. Decrease in variability translates into a gain in statistical power. For some values of success probabilities the drop-the-loser rule has a double advantage over conventional equal allocation in that it has better power and assigns more subjects to the better treatment. Acknowledgments. I thank Stephen Durham, the associate editor, and the referees for their helpful suggestions.     

国有商业银行经营绩效的超产权理论分析

超产权论在产权制度改革的基础上提出了竞争和市场结构对企业治理机制改善的作用.我们把超产权理论的企业产权、竞争、治理机制与绩效相互关系模型引入国有商业银行中,建立市场竞争状态下国有商业银行产权、竞争、治理机制和绩效的理论模型.要提高国有商业银行的经营绩效,构建竞争性的银行体系是关键;竞争绩效的产生还有赖于市场的完善和市场得以有序运作的制度结构的建立与完善.     

An Examination of the Interaction Between Modelling and Its Relationship with Construction Kits: Lessons from the Past and for the Future

Construction kits have played a significant part in nurturing the growth and development of the minds and manipulation-based skills of children (and adults) in formal and non-formal education settings. These kits have origins rooted in the representation of the built world and now have a diversity of form and function, including technical versions with moving parts. This article examines some of the historically based ideas that lie behind the role that kits may have in terms of physical modelling. The article traces the transformation of kits from simple bricks and blocks into more complicated pieces for space-filling and achieving the transfer of forces and motion. This transformation occurred during the Victorian era when the influence of the ideas of educationalists and, perhaps rather strangely, exponents of early aviation, played major roles in determining the diversity of forms of construction kit and modelled possibilities that are now to be seen in classrooms and homes. The article ends with a review of some of the lessons from the past and present that will need to be considered in relation to concrete modelling in schools for the future. This revised version was published online in July 2006 with corrections to the Cover Date.     

政策要闻

原油、成品油进出口配额 将由商务部对外贸易司统管 国务院机构改革以后,我国原油、成品油、化肥等能源产品的进出口配额、进出口权等将全部划归新成立的商务部对外贸易司统一管理。国务院办公厅已发出通知,明确了商务部的14项主要职责,其中第四条为:“研究制定进口商品管理办法和进出口配额计划,确定配额、发放许可证;拟订和执行进出口商品配额招标政策。”