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991.
A robust Bayesian design is presented for a single-arm phase II trial with an early stopping rule to monitor a time to event endpoint. The assumed model is a piecewise exponential distribution with non-informative gamma priors on the hazard parameters in subintervals of a fixed follow up interval. As an additional comparator, we also define and evaluate a version of the design based on an assumed Weibull distribution. Except for the assumed models, the piecewise exponential and Weibull model based designs are identical to an established design that assumes an exponential event time distribution with an inverse gamma prior on the mean event time. The three designs are compared by simulation under several log-logistic and Weibull distributions having different shape parameters, and for different monitoring schedules. The simulations show that, compared to the exponential inverse gamma model based design, the piecewise exponential design has substantially better performance, with much higher probabilities of correctly stopping the trial early, and shorter and less variable trial duration, when the assumed median event time is unacceptably low. Compared to the Weibull model based design, the piecewise exponential design does a much better job of maintaining small incorrect stopping probabilities in cases where the true median survival time is desirably large. 相似文献
992.
Frank Heinemann Rosemarie Nagel Peter Ockenfels 《Econometrica : journal of the Econometric Society》2004,72(5):1583-1599
The theory of global games has shown that coordination games with multiple equilibria may have a unique equilibrium if certain parameters of the payoff function are private information instead of common knowledge. We report the results of an experiment designed to test the predictions of this theory. Comparing sessions with common and private information, we observe only small differences in behavior. For common information, subjects coordinate on threshold strategies that deviate from the global game solution towards the payoff‐dominant equilibrium. For private information, thresholds are closer to the global game solution than for common information. Variations in the payoff function affect behavior as predicted by comparative statics of the global game solution. Predictability of coordination points is about the same for both information conditions. 相似文献
993.
What effect does positive and negative feedback about past risk taking have on the future risk taking of decision makers? The results of an experimental study show that subjects who are led to believe they are very competent at decision making see more opportunities in a risky choice and take more risks. Those who are led to believe they are not very competent see more threats and take fewer risks. The feelings of self-competence and self-confidence on one task did not generalize to a similar task. Perception of opportunities was unexpectedly not related to the perception of threats. As executives bring their personal perceptual biases to firm decision making, our results identify a serious built-in bias in SWOT analysis (the analysis of firms' strengths and weaknesses as related to potential opportunities and threats). Executives who believe that they and their firm are very competent will take more risks and vice versa. Our results also provide evidence that the perceived likelihood of an event depends on whether the event is a loss or a gain. Human decision making is subject to the general bias that outcome expectations are not independent of outcome valuations. 相似文献
994.
Peter T. Ittig 《决策科学》1994,25(4):541-553
This paper presents a model designed to help determine the number of clerks or servers in a retail queuing situation. The model demonstrates a realistic treatment of the effect of waiting time on customer demand and revenues by treating the average waiting time as a form of price. Thus, the demand rate and service level are interrelated. The number of servers is obtained by balancing the cost of additional servers against the revenues and profits arising from greater demand. An example is shown, using data obtained from a supermarket, to demonstrate the insight gained from applying the model. Some extensions and research possibilities are considered, including a treatment of ancillary activities. An appendix examines a continuous version of the model which provides additional insight into the character of the model. 相似文献
995.
Peter Sidebotham 《Child Abuse Review》2000,9(5):311-320
In order to study patterns of child abuse in a pre‐school population, we have looked at children within a local cohort who have been investigated for abuse or placed on the Child Protection Register. This is part of a larger study examining risk and protective factors for child abuse. Of 14 138 children enrolled in the cohort, 329 were investigated for suspected child abuse and 163 were placed on the Child Protection Register over an 8‐year period, representing rates of 10.6 – 23.3 per 10 000 per year. Physical injury and neglect accounted for 31.7% and 29.0% of registrations in the study group respectively, these proportions being similar to those for children of all ages in Avon. In contrast, sexual abuse accounted for 10.9% compared to 21.1% for all ages. Emotional abuse represented just 2.8% of investigations but 25.1% of all registrations in the study group, compared to 14.4% of registrations for all ages. Two hundred and fifty‐five (1.8%) parents reported physical cruelty to their children by themselves or their partner at some stage in the first 3 years; 772 (5.4%) reported some emotional cruelty. The importance of emotional cruelty to children is increasingly being recognized by professionals, but even more so by parents, whose concerns relating to both physical and emotional cruelty are not being identified by current procedures. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
996.
997.
Peter Loader 《Child Abuse Review》1998,7(1):44-57
Shame is a powerful emotion associated with the exposure of any aspect of the self that we wish to keep hidden from others. In its healthy manifestation, shame guards the boundary of the self and promotes a realistic self-appraisal of our capacities and our limitations. However, too much shame results in a sense of the self as fundamentally flawed, and can lead to lifelong problems in living. Shame originates in relationship to others, and most notably by how we are seen as children by our parents. This paper focuses on shame in the family context, the ways shame can be misused in the parent/child relationship and the effects of this on the child. Shame is put forward as an important, but neglected, consideration in child mental health and a core issue in child abuse. The implications for work with children and families are briefly discussed. © 1998 John Wiley & Sons, Ltd. 相似文献
998.
999.
We consider the use of smoothing splines for the adaptive modelling of dose–response relationships. A smoothing spline is a nonparametric estimator of a function that is a compromise between the fit to the data and the degree of smoothness and thus provides a flexible way of modelling dose–response data. In conjunction with decision rules for which doses to continue with after an interim analysis, it can be used to give an adaptive way of modelling the relationship between dose and response. We fit smoothing splines using the generalized cross‐validation criterion for deciding on the degree of smoothness and we use estimated bootstrap percentiles of the predicted values for each dose to decide upon which doses to continue with after an interim analysis. We compare this approach with a corresponding adaptive analysis of variance approach based upon new simulations of the scenarios previously used by the PhRMA Working Group on Adaptive Dose‐Ranging Studies. The results obtained for the adaptive modelling of dose–response data using smoothing splines are mostly comparable with those previously obtained by the PhRMA Working Group for the Bayesian Normal Dynamic Linear model (GADA) procedure. These methods may be useful for carrying out adaptations, detecting dose–response relationships and identifying clinically relevant doses. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
1000.
Maria Francesca Cracolici Miranda Cuffaro Peter Nijkamp 《Statistical Methods and Applications》2009,18(2):275-291
Using spatial econometric models, this paper focuses attention on the spatial structure of provincial unemployment disparities
of Italian provinces for the year 2003. On the basis of findings from the economic literature and of the available socio-economic
data, various model specifications including supply- and demand-side variables are tested. Further we use ESDA analysis as
equivalent to integration analysis on time series; therefore it is applied on each variable, dependent and independent, involved
in the statistical model. The suggestions of ESDA lead us to the most adequate statistical model, which estimates indicate
that there is a significant degree of neighbouring effect (i.e. positive spatial correlation) among labour markets at the
provincial level in Italy; this effect is present notwithstanding we controlled for local characteristics. The unemployment
shows a polarized spatial pattern that is strongly connected to labour demand and to a much lesser extent to the share of
young population and economic structural composition. 相似文献