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51.
This study constructs a simultaneous confidence region for two combinations of coefficients of linear models and their ratios based on the concept of generalized pivotal quantities. Many biological studies, such as those on genetics, assessment of drug effectiveness, and health economics, are interested in a comparison of several dose groups with a placebo group and the group ratios. The Bonferroni correction and the plug-in method based on the multivariate-t distribution have been proposed for the simultaneous region estimation. However, the two methods are asymptotic procedures, and their performance in finite sample sizes has not been thoroughly investigated. Based on the concept of generalized pivotal quantity, we propose a Bonferroni correction procedure and a generalized variable (GV) procedure to construct the simultaneous confidence regions. To address a genetic concern of the dominance ratio, we conduct a simulation study to empirically investigate the probability coverage and expected length of the methods for various combinations of sample sizes and values of the dominance ratio. The simulation results demonstrate that the simultaneous confidence region based on the GV procedure provides sufficient coverage probability and reasonable expected length. Thus, it can be recommended in practice. Numerical examples using published data sets illustrate the proposed methods.  相似文献   
52.
Since the seminal paper by Cook and Weisberg [9 R.D. Cook and S. Weisberg, Residuals and Influence in Regression, Chapman &; Hall, London, 1982. [Google Scholar]], local influence, next to case deletion, has gained popularity as a tool to detect influential subjects and measurements for a variety of statistical models. For the linear mixed model the approach leads to easily interpretable and computationally convenient expressions, not only highlighting influential subjects, but also which aspect of their profile leads to undue influence on the model's fit [17 E. Lesaffre and G. Verbeke, Local influence in linear mixed models, Biometrics 54 (1998), pp. 570582. doi: 10.2307/3109764[Crossref], [PubMed], [Web of Science ®] [Google Scholar]]. Ouwens et al. [24 M.J.N.M. Ouwens, F.E.S. Tan, and M.P.F. Berger, Local influence to detect influential data structures for generalized linear mixed models, Biometrics 57 (2001), pp. 11661172. doi: 10.1111/j.0006-341X.2001.01166.x[Crossref], [PubMed], [Web of Science ®] [Google Scholar]] applied the method to the Poisson-normal generalized linear mixed model (GLMM). Given the model's nonlinear structure, these authors did not derive interpretable components but rather focused on a graphical depiction of influence. In this paper, we consider GLMMs for binary, count, and time-to-event data, with the additional feature of accommodating overdispersion whenever necessary. For each situation, three approaches are considered, based on: (1) purely numerical derivations; (2) using a closed-form expression of the marginal likelihood function; and (3) using an integral representation of this likelihood. Unlike when case deletion is used, this leads to interpretable components, allowing not only to identify influential subjects, but also to study the cause thereof. The methodology is illustrated in case studies that range over the three data types mentioned.  相似文献   
53.
In this interpretive case study the researchers examined the beliefs of 13 self-identifying race-conscious secondary social studies teachers from diverse racial or ethnic, gender, and school-context backgrounds. The researchers found that the teachers' beliefs and views of practice were generally aligned with the main assertions of critical race theory. The teachers described their personal and professional experiences as a major influence on their race-conscious beliefs and views of practice. Moreover, teachers in diverse contexts described having to learn how to navigate the different racial experiences of the students in their classrooms, while teachers in racially segregated contexts (predominately White, Black, or Latino) emphasized the importance of teaching their students about others. Finally, despite the teachers' regular integration of race-related issues into their required and elective courses, they expressed a desire to have more opportunities to teach about race.  相似文献   
54.
广西要想在西部率先全面建成小康社会。必须解决好农业剩余劳动力的转移问题。本文使用抽样法测算广西2008年农业剩余劳动力总数,并按照劳动力转移去向进行统计分析,揭示转移中存在的突出性问题和提出对策建议。  相似文献   
55.
一个民族的文化通常有其系统性与适用的价值观,在当今中西文化交融的时代背景下,作为未来栋梁的大学生选择何种价值观体系,一直受到学术界的普遍关注。借鉴相关价值观研究理论,通过因子分析的方法,归纳出大学生的7个价值观类型,并揭示出大学生社会文化价值观的主要特征,即儒家思想中的进取精神得到了大学生的普遍认同,而极端功利与利己主义受到大学生的强烈排斥,大学生的"自我意识"呈现出不统一的特点,实用主义观念在大学生中广泛存在,传统价值观中的"节俭观"和"宿命论"在大学生中受到了严峻的挑战。  相似文献   
56.
Universities have always competed with one another for the relatively small number of highly qualified students interested in graduate education. This competition has been intensified recently by adverse demographic trends. This paper is concerned with the use of financial aid awards as a means of competition and with allocation of awards so that enrollments are maximized while satisfying academic standards and budget constraints. It also considers the randomness of actual aid disbursements and develops models of incremental aid allocation that increase enrollments but are within tolerance levels for budget overruns.  相似文献   
57.
In this paper we incorporate a linear demand function to model the price-volume causal relationship into stochastic cost-volume-profit (CVP) analysis. We assume that the objective function is to maximize expected profit; other objective functions are also discussed and compared. A linear stochastic model follows from which probabilistic statements can be easily obtained if the random variables are assumed to be multivariate normal. The basic framework is shown to be a special case of project value maximization where project value is the cash flow of the project discounted for time and risk according to the capital asset pricing model. Moreover, an intertemporal extension that considers inventory is developed. In summary, a new approach to stochastic CVP analysis that incorporates the management decision process in an uncertain environment is developed.  相似文献   
58.
Janssen and Daniel analyzed the choice between a one- or a two-point conversion for a particular game situation in college football. Their decision criteria was maximum expected utility based on a von Neumann-Morgenstern utility function defined over the games outcomes. An alternative approach based on a stochastic dominance criterion is presented that does not rely on knowledge of the relative importance of tying vs. winning; rather, it relies on a notion of consistency in the sequential problem.  相似文献   
59.
This note examines the sensitivity of the basic economic-order-quantity inventory model to lot-size errors when holding costs are assumed to be a strictly increasing (though not necessarily linear) function of average inventory. In particular, we show that the penalty associated with ordering either too much or too little is a function not only of the size of the error but of the shape of the holding-cost curve as well. We demonstrate that, under certain conditions, even relatively small lot-size errors can be extremely costly.  相似文献   
60.
This paper attempts to isolate and analyze the principal ideas of multiobjective optimization. We do this without casting aspersions on single-objective optimization or championing any one multiobjective technique. We examine each fundamental idea for strengths and weaknesses and subject two—efficiency and utility—to extended consideration. Some general recommendations are made in light of this analysis. Besides the simple advice to retain single-objective optimization as a possible approach, we suggest that three broad classes of multiobjective techniques are very promising in terms of reliably, and believably, achieving a most preferred solution. These are: (1) partial generation of the efficient set, a rubric we use to unify a wide spectrum of both interactive and analytic methods; (2) explicit utility maximization, a much-overlooked approach combining multiattribute decision theory and mathematical programming; and (3) interactive implicit utility maximization, the popular class of methods introduced by Geoffrion, Dyer, and Feinberg [24] and extended significantly by others.  相似文献   
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