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41.
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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47.
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
48.
49.
Calvyn Potgieter 《International Journal of Technology and Design Education》2004,14(3):205-218
In this article the impact of technology education, as a new learning area (subject) in the curriculum, on in-service teacher
education in South Africa is described in order to ascertain the extent of the impact. The research on which this article
is based draws on a variety of experiences and observations in the field at grassroots level (in particular an outreach project
in rural communities). The envisaged impact of technology education on South African schools, communities, teacher educators
and teachers, the range of in-service teacher education that is required, and the impacts in urban and rural areas are discussed.
Finally a number of concluding remarks are made about the extent of the impact of the inclusion of technology education in
the new National Curriculum Statement and whether the situation has changed since the implementation of a pilot technology
education project in 1998.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
50.
Caroline White Leslie Bank Sean Jones Monga Mehlwana 《Development Southern Africa》1997,14(3):413-423
For a variety of reasons, this article argues, electricity must be seen by policy‐makers in South Africa not as the sole provider of all future household energy needs, but rather as one component of an energy mix which includes such ‘transitional’ fuels as coal, gas and paraffin. The reasons for this are that electricity is expensive for poor households; it is subject to power failures and disconnections for non‐payment; the poor find it difficult to monitor and to control their consumption; appliances are expensive and several are required to make best use of electricity; people prefer other fuels because they are familiar and have strong personal and cultural associations, and because Eskom is not trusted owing to its past ties to illegitimate local authorities and misunderstanding of electricity and how its use is monitored and charged for. Further, it is mistaken to equate ‘development’ with total electrification: most developed countries have fuel mixes which include gas and coal, particularly for cooking and heating. Accepting an affordable fuel mix for the poor in particular would focus attention on the problems currently associated with paraffin, gas and coal, namely fires, poisoning and air pollution. 相似文献