Moments and quadratic forms of matrix variate skew normal distributions

ABSTRACT

In 2007, Domínguez-Molina et al. obtained the moment generating function (mgf) of the matrix variate closed skew normal distribution. In this paper, we use their mgf to obtain the first two moments and some additional properties of quadratic forms for the matrix variate skew normal distributions. The quadratic forms are particularly interesting because they are essentially correlation tests that introduce a new type of orthogonality condition.     

A simple way to deal with multicollinearity

Despite the long and frustrating history of struggling with the wrong signs or other types of implausible estimates under multicollinearity, it turns out that the problem can be solved in a surprisingly easy way. This paper presents a simple approach that ensures both statistically sound and theoretically consistent estimates under multicollinearity. The approach is simple in the sense that it requires nothing but basic statistical methods plus a piece of a priori knowledge. In addition, the approach is robust even to the extreme case when the a priori knowledge is wrong. A simulation test shows astonishingly superior performance of the method in repeated samples comparing to the OLS, the Ridge Regression and the Dropping-Variable approach.     

Reanalysis of Dose-Response Data from the Iraqi Methylmercury Poisoning Episode

Applying a hockey stick parametric dose-response model to data on late or retarded development in Iraqi children exposed in utero to methylmercury, with mercury (Hg) exposure characterized by the peak Hg concentration in mothers'hair during pregnancy, Cox et al. calculated the "best statistical estimate" of the threshold for health effects as 10 ppm Hg in hair with a 95% range of uncertainty of between 0 and 13.6 ppm.⁽¹⁾A new application of the hockey stick model to the Iraqi data shows, however, that the statistical upper limit of the threshold based on the hockey stick model could be as high as 255 ppm. Furthermore, the maximum likelihood estimate of the threshold using a different parametric model is virtually zero. These and other analyses demonstrate that threshold estimates based on parametric models exhibit high statistical variability and model dependency, and are highly sensitive to the precise definition of an abnormal response. Consequently, they are not a reliable basis for setting a reference dose (RfD) for methylmercury. Benchmark analyses and statistical analyses useful for deriving NOAELs are also presented. We believe these latter analyses—particularly the benchmark analyses—generally form a sounder basis for determining RfDs than the type of hockey stick analysis presented by Cox et al. However, the acute nature of the exposures, as well as other limitations in the Iraqi data suggest that other data may be more appropriate for determining acceptable human exposures to methylmercury.     

Changing faces: the story of two Canadian street youth shelters

This study addresses the relationship between street youth shelters and formal child welfare systems in Toronto, Canada. Two case examples, Covenant House (CH) and Youth Without Shelter (YWS), are examined through archival material, participant observations and structured interviews with 21 front-line and managerial shelter workers. The findings suggest that both shelters have formed reciprocal and unequal partnerships with formal child-welfare organisations. The consequences of such an arrangement are threefold: (1) CH and YWS no longer possess an internal environment to support traditional street youths; (2) both shelters have strayed from their original intentions; and (3) many shelter workers express frustration within this dynamic. Several recommendations are put forward to support the survival of youth shelters: advocating increased government daily rates; seeking a balance between building a legitimate public image and an alternative street youth reputation; making every effort to house hard-core street youths; and building innovative internal programmes to act as referral points.     

Volunteerism and social capital in policy implementation: evidence from the Long-Term Care Ombudsman Program

We assess the link between a program's volunteer support and state social capital in the case of the joint implementation of the federal Long-Term Care (LTC) Ombudsman Program by state and federal authorities. This program, which is designed to prevent elder abuse and ensure quality care in long-term facilities, is implemented at the state and local levels and relies heavily on volunteer staff. First, we find that volunteerism is vital to the efficacy of the program's monitoring and investigative functions. Second, we find that volunteerism in this program is tied to broader level conditions of a state's social capital. Last, we discuss the implications of our findings for volunteer-based programs devolved to the states.     

Engaging men as social justice allies in ending violence against women: evidence for a social norms approach

The field of sexual assault prevention is shifting attention to educational interventions that address the role of men in ending violence against women. Recent studies document the often-misperceived norms men hold about other men's endorsement of rape-supportive attitudes and behaviors. The authors provide further evidence supporting the design of population-based social norms interventions to prevent sexual assault. Data from this study suggest that men underestimate the importance that most men and women place on consent and willingness of most men to intervene against sexual violence. In addition, men's personal adherence to only consensual activity and their willingness to act as women's allies are strongly influenced by their perceptions of other men's and women's norms. These findings support the proposition that accurate normative data, which counters the misperception of rape-supportive environments, can be a critical part of comprehensive campus efforts to catalyze and support men's development as women's social justice allies in preventing sexual violence against women.     

Family Grief and Mental Health: A Systemic,Contextual and Compassionate Analysis

Although not always named, grief is central to the experience of mental illness — for people diagnosed, their families and their friends. Yet grief is almost absent from the literature and practice of mainstream psychiatry. This curious fact led to the writing of this article by two workers and a carer, with editorial and political advice from a consumer, as a small step in the direction of integrating perspectives of workers, carers and consumers. It examines the nature of grief associated with mental illness, its impact on family members, and why mainstream mental health services do not directly address it, with suggestions for some therapeutic ways to conceptualise and work with it.     

Talking about Blame

In this analysis particular emphasis is given to the question of blame in meaningful relationships, such as those occurring within families and between practitioners and their clients. The authors suggest there is a potential in these contexts for the subjective experience of being blamed to challenge, perhaps even disturb, an individual's sense of personhood and for interpersonal boundaries to therefore become de-regulated. A general implication for practice is then raised: if blame can be so powerful in its effects, practitioners may benefit from talking explicitly to their clients about blame in order to access intrapsychic and interactional material, for its relevance to the immediacy of the client's lived experience, for its ability to contribute to engagement, and perhaps most importantly, because feeling blamed and being blaming reduces the self-agency available to clients and hence potential for change.     

Realizing Benefits from Enterprise Resource Planning: Does Strategic Focus Matter?

A key driver of the recent wave of enterprise resource planning (ERP) implementations was the assumption that the integration of business information would provide firms with a competitive advantage, yet concrete business benefits have been uneven across adopting firms. A possible explanation is that although the resource‐based view holds that competitive advantage is derived from inimitable resources, ERP software has become a commodity. Socio‐technical theory suggests that internal organizational resources based on a foundation of ERP technology may be the true drivers of ERP benefits. A firm's strategic configuration is posited to influence the portfolio of organizational competencies available to leverage the benefits of integrated business information, and a number of hypotheses are developed based on the notion that firms with different strategic objectives will realize different operational benefits from the adoption of ERP systems. Survey data from North American manufacturing firms that have implemented ERP systems demonstrate that ERP adopters seeking operational performance improvements are likely to realize these benefits. On the other hand, those seeking external market and supply chain performance improvements must first establish a foundation of internal operational performance improvements before customer satisfaction and supply chain benefits can be realized.