Bayesian networks for imputation

Summary.  Bayesian networks are particularly useful for dealing with high dimensional statistical problems. They allow a reduction in the complexity of the phenomenon under study by representing joint relationships between a set of variables through conditional relationships between subsets of these variables. Following Thibaudeau and Winkler we use Bayesian networks for imputing missing values. This method is introduced to deal with the problem of the consistency of imputed values: preservation of statistical relationships between variables ( statistical consistency ) and preservation of logical constraints in data ( logical consistency ). We perform some experiments on a subset of anonymous individual records from the 1991 UK population census.     

Semi-empirical likelihood inference for the ROC curve with missing data

The receiver operating characteristic (ROC) curve is one of the most commonly used methods to compare the diagnostic performance of two or more laboratory or diagnostic tests. In this paper, we propose semi-empirical likelihood based confidence intervals for ROC curves of two populations, where one population is parametric and the other one is non-parametric and both have missing data. After imputing missing values, we derive the semi-empirical likelihood ratio statistic and the corresponding likelihood equations. It is shown that the log-semi-empirical likelihood ratio statistic is asymptotically scaled chi-squared. The estimating equations are solved simultaneously to obtain the estimated lower and upper bounds of semi-empirical likelihood confidence intervals. We conduct extensive simulation studies to evaluate the finite sample performance of the proposed empirical likelihood confidence intervals with various sample sizes and different missing probabilities.     

对马克思主义理论整体性问题研究的反思及其现实意义

整体性是马克思主义理论的重要特性,整体性问题是研究马克思主义的一个基本问题,也是当前我国学者研究马克思主义的一个热点问题。我国理论界围绕此问题进行了深入而系统的研究,取得了丰硕成果,但也存在一些问题,对这些问题的反思,有益于进一步实现马克思主义整体发展和创新的前瞻性使命。     

Variance estimation when donor imputation is used to fill in missing values

Donor imputation is frequently used in surveys. However, very few variance estimation methods that take into account donor imputation have been developed in the literature. This is particularly true for surveys with high sampling fractions using nearest donor imputation, often called nearest‐neighbour imputation. In this paper, the authors develop a variance estimator for donor imputation based on the assumption that the imputed estimator of a domain total is approximately unbiased under an imputation model; that is, a model for the variable requiring imputation. Their variance estimator is valid, irrespective of the magnitude of the sampling fractions and the complexity of the donor imputation method, provided that the imputation model mean and variance are accurately estimated. They evaluate its performance in a simulation study and show that nonparametric estimation of the model mean and variance via smoothing splines brings robustness with respect to imputation model misspecifications. They also apply their variance estimator to real survey data when nearest‐neighbour imputation has been used to fill in the missing values. The Canadian Journal of Statistics 37: 400–416; 2009 © 2009 Statistical Society of Canada     

Quantitative Risk Estimation for a Legionella pneumophila Infection Due to Whirlpool Use

Quantitative microbiological risk assessment was used to quantify the risk associated with the exposure to Legionella pneumophila in a whirlpool. Conceptually, air bubbles ascend to the surface, intercepting Legionella from the traversed water. At the surface the bubble bursts into dominantly noninhalable jet drops and inhalable film drops. Assuming that film drops carry half of the intercepted Legionella, a total of four (95% interval: 1–9) and 4.5×10⁴ (4.4×10⁴ – 4.7×10⁴) cfu/min were estimated to be aerosolized for concentrations of 1 and 1,000 legionellas per liter, respectively. Using a dose‐response model for guinea pigs to represent humans, infection risks for active whirlpool use with 100 cfu/L water for 15 minutes were 0.29 (～0.11–0.48) for susceptible males and 0.22 (～0.06–0.42) for susceptible females. A L. pneumophila concentration of ≥1,000 cfu/L water was estimated to nearly always cause an infection (mean: 0.95; 95% interval: 0.9–～1). Estimated infection risks were time‐dependent, ranging from 0.02 (0–0.11) for 1‐minute exposures to 0.93 (0.86–0.97) for 2‐hour exposures when the L. pneumophila concentration was 100 cfu/L water. Pool water in Dutch bathing establishments should contain <100 cfu Legionella/L water. This study suggests that stricter provisions might be required to assure adequate public health protection.     

中国行政管理学研究状况的文献计量学分析

采用文献计量学方法从研究主题、研究方式、研究阶段三个角度对2001-2005年刊登在中国行政管理学4个重要刊物上的研究论文的内部结构所进行的分析发现,在行政管理学的研究主题上,行政职能、决策、改革、哲学、法治、人事、基层政权为主流研究领域;行政职能、行政决策、行政改革、国外行政研究和行政哲学等为一级主题的研究热点;公共服务、绩效评估、政府信用、服务型政府和非政府组织等为二级主题的研究热点.在研究方式上,中国行政管理学研究存在着经验研究与非经验研究、定性分析与定量分析的比例失调问题,但经验研究与定量分析方法正在得到越来越多的应用.在研究阶段上,所调查的研究论文多处于问题描述、问题诊断和对策分析阶段.     

坚持从战略全局观察与处理中日关系

与经济领域的热火场面相比,在政治以及安全领域,近来中日关系不断遭遇冷风。从本质上看,“经热政冷”的状况是由冷战后日本国家利益和战略选择的结构性矛盾造成的;同时,与近年来美国对日政策的调整有着密切关系,也离不开日本的国内因素影响。“政冷”的发展,日益严重地制约了“经热”,而且由于中日关系的“政冷”已由历史认识和外交层面的矛盾,提升到安全领域的摩擦,这更使“政冷”日趋危险。为了避免发生有违于中日根本利益的冲突,必须从战略全局来观察与处理中日关系。     

四川省属高校大学生思想政治热点问题调查与研究

高校大学生思想政治工作是提升高校办学实力和办学质量的重要保障,大学生关注的思想政治热点问题一定程度上制约着高校思想政治工作的着力点。对省属高校大学生思想政治热点问题调查与研究,除了能有效提升参与大学生的实践能力和创新精神外,还能为高校思想政治工作提出策略和建议。     

Minority Elder Maltreatment:

Comparison of 126 minority and 161 non-minority instances of elder maltreatment produces no compelling profile of differences, although there are implications for both study and practice. Within the minority subsample, differences in ethnic group, gender, age, and income provide some information. Hispanics have a less developed social support system, female-male distinctions focus on mortality rate and maltreatment type differences, the oldest old appear to differ from younger elder groups in several respects, and the poor may form a subgroup of isolates or loners.     

镁对热浸镀铝件耐腐蚀性能的影响

通过向热浸镀铝液中加入微量Mg,分析了热浸镀铝层中Mg含量对镀件在不同化学介质中耐腐蚀性能的影响.结果表明,适量Mg可以提高镀件在盐水和弱碱性水溶液中的耐腐蚀性,而对强酸和强碱水溶液,Mg的加入不能提高镀件的耐腐蚀性能,通过分析Mg在镀层中的分布及对合金层第二相的影响,探讨了产生这种影响的原因.