Testing equality of two normal covariance matrices with monotone missing data

Abstract

The problem of testing equality of two multivariate normal covariance matrices is considered. Assuming that the incomplete data are of monotone pattern, a quantity similar to the Likelihood Ratio Test Statistic is proposed. A satisfactory approximation to the distribution of the quantity is derived. Hypothesis testing based on the approximate distribution is outlined. The merits of the test are investigated using Monte Carlo simulation. Monte Carlo studies indicate that the test is very satisfactory even for moderately small samples. The proposed methods are illustrated using an example.     

Random effects regression mixtures for analyzing infant habituation

Random effects regression mixture models are a way to classify longitudinal data (or trajectories) having possibly varying lengths. The mixture structure of the traditional random effects regression mixture model arises through the distribution of the random regression coefficients, which is assumed to be a mixture of multivariate normals. An extension of this standard model is presented that accounts for various levels of heterogeneity among the trajectories, depending on their assumed error structure. A standard likelihood ratio test is presented for testing this error structure assumption. Full details of an expectation-conditional maximization algorithm for maximum likelihood estimation are also presented. This model is used to analyze data from an infant habituation experiment, where it is desirable to assess whether infants comprise different populations in terms of their habituation time.     

双波长比值法测定水杨酸、间苯二酚、对氨基苯甲酸的含量

依据水杨酸、间苯二酚、对氨基苯甲酸三组分的比值光谱特征,以对氨基苯甲酸为干扰组分,选择241nm、278nm作为测定水杨酸的波长;以水杨酸作为干扰组分,选择214nm、240nm作为测定间苯二酚的波长;以间苯二酚作为干扰组分,选择222nm、279nm作为测定对氨基苯甲酸的波长.结果显示,水杨酸浓度在1~80mg/L,基本二酚浓度在0.8~40mg/L,对氨基苯甲酸浓度在0.4~40mg/L范围内具有良好的线性关系.本方法具有测定波长少,光谱分离能力强、计算简单、能在低档分光光度计上实现、易于推广等特点.     

Visualization of generalized mean estimators using auxiliary information in survey sampling

Abstract

The mean estimators with ratio depend on multiple auxiliary variables and unknown parameters in a finite population setting. We propose a new generalized approach with matrices for modeling the mutivariate mean estimators with two auxiliary variables. Our approach brings naturally a graphical analysis for comparing mean estimators.     

Sex Related Factors in the Perception of Threatening Facial Expressions

This study replicated and extended previously reported sex differences involving both viewer and target in the recognition of threatening facial expressions. Based on the assumption that the evolved cognitive mechanisms mediating anger recognition would have been designed by natural selection to operate quickly in the interests of survival, brief tachistoscopic presentation of stimulus photographs was used. Additionally, in contrast to prior published studies, the statistical methods of signal detection research were used to control for the confounding effects of non-random guessing. The main hypothesis, that anger posed by males would be more accurately perceived than anger posed by females, was supported. A secondary hypothesis, that female-posed anger would be more accurately perceived by women than by men, received partial support. Testosterone levels, measured inferentially in terms of diurnal cycles, failed to show the hypothesized positive relationship to accuracy of anger perception.     

Comprehensive neighbourhood mapping: developing a powerful tool for child protection

This paper proposes ‘comprehensive neighbourhood mapping’ as a schema for gathering and interpreting information within a given geographical area which is informed by imaginative thinking about the safety of children and young people from sexual crime. It would build upon current forms of profiling by local authorities, health authorities and central Government. CNM would actively involve local people, in partnership with agencies, in ‘mapping’ danger points and support points. Eight components are discussed, including environmental issues, locations of sex offenders, sites where teenagers meet and share information, supportive individuals and organizations. Some issues for pilot projects are discussed, including the need to set up planning and implementation groups and to integrate CNM into wider child protection and community safety strategies. CNM is grounded in an ecological perspective which sees partnership approaches as essential and believes an overarching view of neighbourhood needs, based on detailed local information and understanding of how different forms of harm interconnect, is crucial in developing child protection strategies. At times of acute official anxiety about community ‘lynch‐mob’ reactions to known paedophiles, CNM aims to build communities which instead are informed and thoughtful about child protection. Copyright © 2002 John Wiley & Sons, Ltd.     

上证30指数股市盈率实证分析

通过对2000年上证30指数股市盈率水平及其影响因素进行实证分析,可以发现,其中股息支付率、每股收益增长率、行业平均市盈率对股票P/E值起主要的解释作用,而股本规模因素,解释力却有限,除每股收益增长率外,各变量的相关性与理论分析基本一致.     

社会性别与深层道德结构--择偶、性的道德模式

在男权文化占主导地位的社会环境中,男女在择偶和性的道德模式上存在着完全不对等的规范,男女占有不同的社会资源,这些被长久地视为自然而然、合情合理的现象。文章试图从社会性别视角来探究隐藏在择偶和性风俗习惯背后的不平等的道德模式。     

建国初期有组织犯罪惩治策略研究--一种犯罪学的分析路径

有组织犯罪日益猖獗已成为国际关注的社会问题。我国 97刑法增设了黑社会性质组织罪条款 ,作出了立法反应。对这种特殊形态的犯罪如何有效地惩治与防范 ,已是急迫而艰巨的任务 ,也是犯罪学极富价值的课题。从建国初期新生政权惩治有组织犯罪的策略其效用来看 ,对当代中国惩治有组织犯罪实践有三个方面的启示 :国家与社会双本位控制 ;打击与促进社会整合相结合 ;宽严相济的灵活的刑事政策有利于分化瓦解有组织犯罪。     

出走“娜拉”的尴尬——现代爱情喜剧的性别透视

“娜拉”出走后的沉浮遭际,构成了中国现代爱情喜剧的主要题材特色。文章在归纳了中国现代爱情喜剧的发展线索之后,从社会性别角度,透视了出走“娜拉”的诸多尴尬与无奈。