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.     

Professional blinders? The novel as an eye-opener in organizational analysis

ABSTRACT

Scholarly textbooks often follow a logic where suitable empirical cases are selected to illustrate the theoretical and analytical points that we as scholars want to make. But what would happen if we would do the opposite: build a textbook on a novel written by a novelist for such purpose and let the theories explain the actions and emotions of fictional characters? In this article, we share and reflect upon our experiences of co-authoring a textbook in organization theory together with a professional novelist. We argue that the novel can function as an eye-opener in organizational analysis, forcing us to look beyond more static and rationalistic perspectives on organizations as well as the stereotypes of such. We build and relate our experiences to the growing literature about using fiction in scholarly work and discuss the potential of such genre-bending work when we bring in flesh and blood into the analyses.     

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.     

Maternal and paternal reactions to child sadness predict children's psychosocial outcomes: A family‐centered approach

Parents' reactions to children's emotions shape their psychosocial outcomes. Extant research on emotion socialization primarily uses variable‐centered approaches. This study explores family patterns of maternal and paternal responses to children's sadness in relation to psychosocial outcomes in middle childhood. Fifty‐one families with 8‐ to 12‐year‐old children participated. Mothers and fathers reported their reactions to children's sadness and children's social competence and psychological adjustment. Cluster analyses revealed three family patterns: Supportive (high supportive and low non‐supportive reactions from both parents), Not Supportive (low supportive reactions from both parents), and Father Dominant (high paternal supportive and non‐supportive reactions, low maternal supportive and non‐supportive reactions). Supportive families had children with higher social competence and more internalizing symptoms whereas Father Dominant families had children with lower social competence and fewer internalizing symptoms. Not Supportive families had children with average social competence and fewer internalizing symptoms. Findings are discussed in relation to the “divergence model” which proposes that a diverse range of parental responses to children's sadness, rather than a uniformly supportive approach, may facilitate children's psychosocial adjustment.     

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.     

Childbearing and Marriage: Investigating the Importance of Context for Meaning-Making of First-Time Marriage

Previous research reveals that the temporal ordering of childbearing and marriage can have an impact on the meaning of first-time marriage. This article aims to obtain a deeper understanding of meaning-making of first-time marriage in relation to childbearing. Narrative interviews with 16 brides and grooms in 8 couples in Sweden were conducted. The material was analyzed in relation to the temporal ordering of childbearing and marriage. The study reveals that the construction of meaning of marriage does not only relate to the temporal context. Social factors such as social class or family formation might also be relevant for how meaning is constructed. This article contributes to a deeper understanding of meaning-making as a relational process constructed within particular contexts.     

Contextual identity experiencing facilitates resilience in Native American academics

This article discusses the socio-cultural dynamics that interact with ethno-racial identity experiencing in a previously under-researched group. A qualitative interdisciplinary study with 40 Native American academics from 28 mainstream universities across the U.S. served as a case example with findings that contrasted with historically influential theoretical frameworks postulating identity confusion and conflicts at the intersection of one’s mainstream education and profession versus one’s ethno-racial community grounding. Instead of feeling pressure to identify with only one worldview, the contextual, dynamic identities associated with the inclusive and flexible self-concept of tribal participants allowed them to in turn take advantage of two divergent cultural meaning systems pertaining to their distinct socio-cultural contexts. These shifts were experienced as not endogenous but rather exogenous variables, which did not cause the historically theorized issues. Participants felt their tribal identities instead facilitated meaningful integration of the existing incongruences, which resulted in unexpectedly resilient subjective experiencing.     

Stigma, HIV/AIDS and prevention of mother-to-child transmission in Zambia

This report evaluates the extent of perceived and enacted HIV/AIDS-related stigma in a rural setting in Zambia. Stigmatisation is abundant, ranging from subtle actions to the most extreme degradation, rejection and abandonment. Women with HIV and pregnant women assumed to be HIV positive are repeatedly subjected to extensive forms of stigma, particularly once they become sick or if their child dies. Despite increasing access to prevention of mother to child transmission initiatives, including anti-retroviral drugs, the perceived disincentives of HIV testing, particularly for women, largely outweigh the potential gains from available treatments. HIV/AIDS related stigma drives the epidemic underground and is one of the main reasons that people do not wish to know their HIV status. Unless efforts to reduce stigma are, as one peer educator put it, “written in large letters in any HIV/AIDS campaign rather than small”, stigma will remain a major barrier to curbing the HIV/AIDS pandemic.