The power of the circular cone test: A noncentral chi-bar-squared distribution

Pincus (1975) derived the null distribution of the likelihood-ratio test statistic for testing that the mean vector of a multivariate normal distribution is zero against the alternative that the mean vector lies in a circular cone. Under the null hypothesis, the likelihood-ratio test statistic has a chi-bar-squared distribution. We extend the results of Pincus by deriving the distribution of the likelihood-ratio test statistic under the alternative hypothesis. In a special case, the distribution is a “noncentral chi-bar-squared” distribution. To our knowledge, this is the first order-restricted testing problem for which the relationship between the null and alternative distributions of the test statistic is similar to the relationship in the linear-model setting. That is, the distribution of the likelihood-ratio test has a central form of a distribution under the null hypothesis and a noncentral form of the same distribution under the alternative.     

Goodness-of-fit test for uniform stochastic ordering among several distributions

The likelihood-ratio test (LRT) is considered as a goodness-of-fit test for the null hypothesis that several distribution functions are uniformly stochastically ordered. Under the null hypothesis, H₁ : F₁ ? F₂ ?···? F_N, the asymptotic distribution of the LRT statistic is a convolution of several chi-bar-square distributions each of which depends upon the location parameter. The least-favourable parameter configuration for the LRT is not unique. It can be two different types and depends on the number of distributions, the number of intervals and the significance level α. This testing method is illustrated with a data set of survival times of five groups of male fruit flies.     

Failure and maintenance data extraction from power plant maintenance management databases

Reliability analysis is plagued by a lack of accurate data, leading to suboptimal parameter estimates and inaccurate decisions about replacement intervals and preventive maintenance activities. This paper discusses some of the problems associated with failure and maintenance data extraction from coal-fired power plant maintenance databases. Data from four generating units were observed for over 5 years and a reasonable number of equipment classes reviewed. The coal mills are identified as significant equipment that affects the availability of the generating units. This paper describes the interplay of events which includes failure modes, failure, repair and operating time. We investigate a database showing operation of coal mills, and give an exploratory data analysis in which we investigate engineering hypotheses related to mill operation. A competing risk probability model is proposed which captures some of the observed features of the systems under study.     

Language and libertarianism: the politics of cyberculture and the culture of cyberpolitics

A significant number of theories concerning the nature of cyberspace or virtuality are being constructed with little regard for the empirical realities of online life. This article sets out certain simple empirical factors related to the nature first of politics in cyberspace and second culture in cyberspace. These questions are posed as ‘what is the politics of cyberculture?’ and ‘what is the culture of cyberpolitics?’. The politics of cyberculture revolves around issues of grossly uneven regional distribution of the Internet and a bias toward anglo‐american language and culture that is based on the competitive individual. The culture of cyberpolitics revolves around informational forms of libertarian and anarchist ideologies that posit cyberspace as the realm of individual freedom. These cultures and politics can be related to each other as the structure and action of cyberspace. The assumption that cyberspace is constituted by individuals is revealed as an assumption of both, and connection between, cyberpolitics and cybercultures.     

A Shelter-Based Stress-Reduction Group Intervention Targeting Self-Esteem, Social Competence, and Behavior Problems Among Homeless Children

It has been estimated that families with children now account for 40% of the population who become homeless. Given the consistency of research showing the potentially damaging effects of homelessness as a stressor upon the social and emotional development of children, the question of importance is how to best intervene to reduce the likelihood or severity of such possible negative consequences. The approach taken here involved the development of a Shelter-Based Stress-Reduction Group Intervention Targeting Self-Esteem and Behavior Problems Among Homeless Children.Data were collected on 52 elementary-school–age children from family-shelter facilities in Central Florida. The child's level of psychosocial functioning was assessed using the Coopersmith Self-Esteem Inventory (CSEI) and Achenbach's Child Behavior Checklist (CBCL). Although the repeated measures ANOVA techniques applied to those subjects were nonsigni-ficant, the relatively small sample size in study conditions led to consideration of the magnitude of effect sizes obtained in treatment and comparison groups. The changes in the intervention group's mean scores on key psychosocial outcome variables of interest were consistent with hypotheses, providing suggestive evidence of the potential utility of stress management training.     

Mixed Results, Lousy Process: the Management Experience of Organizational Change

This paper reports the findings of a survey of 92 managers, from 14 public and 14 private-sector organizations. The aim was to explore the experience of change, extending the findings of a previous study (Buchanan, Claydon and Doyle, 1999). The survey addressed six themes: communication, evaluation, learning, attitudes and relationships, implementation and change and continuity. Overall, the results present a bleak picture of the process and outcomes of contemporary change. Most managers claim that change responsibility affords valuable personal learning. However, recent change has also been accompanied by stress, work intensification, command and control and management–employee distrust. A comparison of public and private–sector responses suggests that the experience of change in the public sector has been more pressured than in the private sector. Comparison of responses by management level indicates that senior managers are more likely to hold positive views of the change process and its outcomes. Explanations for these differences in experience and perception are considered, along with the implications. It is concluded that an adequate theory of organizational change must address the contradictions and tensions in the lived experience of those implicated, and that effective practice should consider the linkage of change implementation with organizational learning mechanisms which, on this evidence, are absent.     

Contingency Learning and Reactivity in Preterm and Full‐Term Infants at 3 Months

Learning difficulties in preterm infants are thought to reflect impairment in arousal regulation. We examined relationships among gestational age, learning speed, and behavioral and physiological reactivity in 55 preterm and 49 full‐term infants during baseline, contingency, and nonreinforcement phases of a conjugate mobile paradigm at 3 months corrected age. For all infants, negative affect, looking duration, and heart rate levels increased during contingency and nonreinforcement phases, whereas respiratory sinus arrhythmia (RSA, an index of parasympathetic activity) decreased and Cortisol did not change. Learners showed greater RSA suppression and less negative affect than nonleamers. This pattern was particularly evident in the preterm group. Overall, preterm infants showed less learning, spent less time looking at the mobile, and had lower Cortisol levels than full‐term infants. Preterm infants also showed greater heart rate responses to contingency and dampened heart rate responses to nonreinforcement compared to full‐term infants. Findings underscore differences in basal and reactivity measures in preterm compared to full‐term infants and suggest that the capacity to regulate parasympathetic activity during a challenge enhances learning in preterm infants.     

Collaborate or Compete: Examining Manufacturers' Replacement Strategies for a Substance of Concern

The recent proliferation of media reports on substances of concern has increased consumer fears, sparked scientific debate, and highlighted the need for stronger chemical regulations. When a substance of concern is identified (e.g., bisphenol‐A (BPA) in reusable water bottles), manufacturers face difficult trade‐offs in deciding whether to proactively replace the substance in their products or to defer replacement and wait to see if regulation occurs. In this study, we examine when opportunities exist for manufacturers to avoid competitively replacing (i.e., making their replacement decisions on their own), and instead, collaborate to replace a substance of concern. We model a vertically differentiated market consisting of a high‐end manufacturer and a low‐end manufacturer, both of whom sell a product that contains a substance of concern. Our analysis investigates how market dynamics (competition and consumer preferences) and external factors (replacement costs and regulatory uncertainty) influence manufacturers' collaboration, replacement, and pricing decisions. We find that when the manufacturers do not collaborate, the high‐end manufacturer can use the presence of a substance of concern to dominate the market by capturing more demand and often charging a higher price for his product than the low‐end manufacturer. Collaboration is possible when there is either a shared fixed cost savings for both manufacturers or an opportunity for the low‐end manufacturer to benefit his competitive position by motivating the high‐end manufacturer to collaborate. From a consumer perspective, although collaboration reduces consumer exposure to the substance of concern, it can decrease consumer surplus when the replacement substance is very expensive.     

ARE WE TOO BUSY TO VOLUNTEER? THE RELATIONSHIP BETWEEN TIME AND VOLUNTEERING USING THE 1997 ABS TIME USE DATA

Time availability is a key concept in relation to volunteering, leading to organisations and governments targeting those outside paid work as a potential source of volunteers, it may be that factors such as a growth in female participation in the labour market and an increase in work hours will lead to more people saying they are simply too busy to volunteer. This paper discusses how social and economic change, such as changing work patterns, are impacting on time availability. Using the 1997 ABS Time Use data, it identifies a predictive model of spare time by looking at demographic, life stage and employment related variables. Results confirm that those outside paid work, particularly the young, males and those without partners or children, are the groups most likely to have time to spare. These groups do not currently report high rates of volunteering. The paper concludes by questioning the premise that people will volunteer simply because they have time to spare. This is just one component of a range of motivations and factors that influence the decision to volunteer.