Adaptive Bayesian compound designs for dose finding studies

We consider the problem of how to efficiently and safely design dose finding studies. Both current and novel utility functions are explored using Bayesian adaptive design methodology for the estimation of a maximum tolerated dose (MTD). In particular, we explore widely adopted approaches such as the continual reassessment method and minimizing the variance of the estimate of an MTD. New utility functions are constructed in the Bayesian framework and are evaluated against current approaches. To reduce computing time, importance sampling is implemented to re-weight posterior samples thus avoiding the need to draw samples using Markov chain Monte Carlo techniques. Further, as such studies are generally first-in-man, the safety of patients is paramount. We therefore explore methods for the incorporation of safety considerations into utility functions to ensure that only safe and well-predicted doses are administered. The amalgamation of Bayesian methodology, adaptive design and compound utility functions is termed adaptive Bayesian compound design (ABCD). The performance of this amalgamation of methodology is investigated via the simulation of dose finding studies. The paper concludes with a discussion of results and extensions that could be included into our approach.     

从中西思维差异谈美学的研究态度

重“理论”与重“实用”体现了中西传统思维差异的一个方面,这一差异使中西学术走上了两条不同的道路,同时也证实了理论学科强大的生命力。对这一差异及其产生的结果的研究为美学发展应采取的学术态度提供了借鉴。     

当前我国出生性别比异常的经济学思考

我国出生性别比偏高的问题近几年愈演愈烈,被广泛关注的范围已经从学术界扩大了整个社会。本文拟就从产生问题的根源——男孩偏好以及隐藏在其背后的男女孩儿预期效用迥异入手,提出对当前已有政策的一些修正方案。笔者认为:诚如许多专家学者指出,问题产生的根本原因是文化因素——男孩偏好,但是问题解决的根本出路绝不能仅限于男女平等,而应该实行对女孩的积极的性别歧视。     

Rethinking Risk Attitude: Aspiration as Pure Risk

There exists no completely satisfactory theory of risk attitude in current normative decision theories. Existing notions confound attitudes to pure risk with unrelated psychological factors such as strength of preference for certain outcomes, and probability weighting. In addition traditional measures of risk attitude frequently cannot be applied to non-numerical consequences, and are not psychologically intuitive. I develop Pure Risk theory which resolves these problems – it is consistent with existing normative theories, and both internalises and generalises the intuitive notion of risk being related to the probability of not achieving one’s aspirations. Existing models which ignore pure risk attitudes may be misspecified, and effects hitherto modelled as loss aversion or utility curvature may be due instead to Pure Risk attitudes.     

A Note on Consistency in Utility Assessment*

A methodology for determining a von Neumann-Morgenstern utility function is outlined based on the axioms crucial to such a function. Reconciliation of inconsistent judgments is facilitated using the theory of reciprocal matrices. Numerical measures of the collective divergence of a set of judgments from perfect consistency or coherency are provided.     

ON THE SENSITIVITY OF BRAND-CHOICE SIMULATIONS TO ATTRIBUTE IMPORTANCE WEIGHTS

This paper critically reviews the report by Green, DeSarbo, and Kedia “on the insensitivity of brand-choice simulations to attribute importance weights”. The review suggests that results from two of their four weight distortion conditions should be viewed with suspicion and that their procedure for selecting brand scores biased the sensitivity analysis and inflated individual-level hit rates. The most unfortunate problem is that their simulation-experimental design precludes a global test of the main research issue. Results are presented from an alternative simulation approach that has the power to detect the sensitivity of brand shares to a wide range of conditions that affect the shape of attribute weight distributions. The results suggest that conclusions of Green, DeSarbo, and Kedia apply only to a limited domain and would not obtain in many likely market situations. Extensions to nonadditive decision structures are suggested and several unresolved issues are outlined.