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51.
A play-the-winner-type urn design with reduced variability 总被引:1,自引:0,他引:1
Anastasia Ivanova 《Metrika》2003,58(1):1-13
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. 相似文献
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53.
Daniel Sgroi 《Experimental Economics》2003,6(2):159-180
Herding describes the phenomenon in decision-making where an economic agent disregards his own private information to follow the actions of his predecessors as in Banerjee (1992). With later decision-makers simply copying earlier decisions their private information cannot be inferred by other decision-makers and will be forever lost. There is some experimental evidence on simple sequential herding of this type in the literature, notably Anderson and Holt (1997). This paper differs by allowing subjects to delay their decision-making in order to benefit from observing others' actions as in more recent herding models such as Chamley and Gale (1994). The results in this paper suggest that subjects will indeed delay when their private information is not sufficiently strong. Despite this ability to wait, as predicted in the theoretical literature, cascades remained ubiquitous and more worrying still, reverse-cascades occurred in which incorrect decisions made by early decision-makers produced informational cascades on the wrong action. In an alternative design, informing subjects that they had made incorrect choices only made matters worse as subjects moved further away from rational behavior. 相似文献
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The performance of service industries in Canada has been lower than that of good industries over the last four decades, with noticeable exceptions such as for railways and telecommunication carriers. Service industries were less economically (and technically) efficient in that they generated less output value (quantity) per hour worked (level and growth) or per combined unit of labour and capital (multifactor productivity growth) than good industries. The relative output price of services declined slightly over time compared with goods. At the disaggregated level, changing relative output prices were substantial and proved to be an important factor explaining the relative satisfactory economic performance of many service industries despite their low technical performance. Nevertheless, the output share of service industries increased over that period, sustained, mainly, by the growing recourse of all firms to outsourcing of services. 相似文献
59.
Eric F. Parkinson 《International Journal of Technology and Design Education》2004,14(3):219-243
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. 相似文献
60.
This paper examines the influence of institutional differences on corporate risk management practices in the USA and the Netherlands. We compare results to surveys in each country using a strategy that corrects for differences over industry and size classes across the Dutch and US samples. We document several differences in the firms’ uses and attitudes towards derivatives and attempt to attribute them to the differences in the institutional environments between the USA and the Netherlands. We find that institutional differences appear to have an important impact on risk management practices and derivatives use across US and Dutch firms. 相似文献