Sequential design of computer experiments for the estimation of a probability of failure

This paper deals with the problem of estimating the volume of the excursion set of a function f:ℝ ^d →ℝ above a given threshold, under a probability measure on ℝ ^d that is assumed to be known. In the industrial world, this corresponds to the problem of estimating a probability of failure of a system. When only an expensive-to-simulate model of the system is available, the budget for simulations is usually severely limited and therefore classical Monte Carlo methods ought to be avoided. One of the main contributions of this article is to derive SUR (stepwise uncertainty reduction) strategies from a Bayesian formulation of the problem of estimating a probability of failure. These sequential strategies use a Gaussian process model of f and aim at performing evaluations of f as efficiently as possible to infer the value of the probability of failure. We compare these strategies to other strategies also based on a Gaussian process model for estimating a probability of failure.     

Multivariate Pareto Distributions: Inference and Financial Applications

Univariate Pareto distributions are extensively studied. In this article, we propose a Bayesian inference methodology in the context of multivariate Pareto distributions of the second kind (Mardia's type). Computational techniques organized around Gibbs sampling with data augmentation are proposed to implement Bayesian inference in practice. The new methods are shown to work well in artificial examples involving a trivariate distribution, and to an empirical application involving daily exchange rate data for four major currencies.     

The impacts of climate variability on household welfare in rural Mexico

In light of the expected increase in weather variability from climate change, we examine the impact of weather shocks, defined as rainfall or growing degree days more than a standard deviation from their respective long-run means, on household consumption per capita. The analyses suggest that both rainfall and temperature shocks affect both food and non-food consumption. Furthermore, the results show that a household’s ability to protect its consumption from weather shocks depends on the climate region and when in the agricultural year the shock occurs. Especially, households in arid climates are not fully protected from weather shocks occurring during the beginning of the wet season (April, May, June). The results highlight the necessity to account for the underlying climatic variation as well as to carefully define the shocks.     

Anal Cancer Screening: Barriers and Facilitators Among Ethnically Diverse Gay, Bisexual, Transgender, and Other Men Who Have Sex With Men

Knowledge and beliefs about anal cancer screening among gay and other men who have sex with men remains unclear, despite data that suggests significant risk for intra-anal HPV-related cancers. Nevertheless, community-based screening activities may be most effective when stake-holder perspectives are addressed. We conducted four focus groups among 16 male and 3 female health care advocates experienced in working with diverse gay and other men who have sex with men in Los Angeles. Barriers to anal cancer screening included lack of awareness, stigma, psychological and physical discomfort, the anus as hidden/private, primary concern with HIV, and men's lack of healthcare seeking. Facilitators were community screening sites, novel strategies such as home testing, health care system changes and targeted educational campaigns, which may increase anal cancer awareness and screening among ethnically diverse men who have sex with men.     

Ownership and Control in Closely‐held Family‐owned Firms: An Exploration of Strategic and Operational Control

Much of the existing research into the divorce of ownership and control either focuses on the propensity for the separation of decision functions or upon scrutinizing conceptions, gauges or the practicalities of organizational control in large corporations. Although far from equivocal, such research appears broadly to concur that where ownership is dispersed, de facto control is likely to be exerted by management and that where ownership is closely‐held, de facto as well as legal control is exerted by owners. This study examines this assumption through exploring the nature of control in a closely‐held family firm. In this regard, the focus of this study is not on consequences of divorced ownership and control but rather on exploring the contingencies where ownership and control diverge. This research reveals a case wherein a closely‐held family firm is strategically and operationally controlled by its managers. Case research leads to the development of a range of insights regarding the owner/family and the management characteristics that contribute to this scenario. The paper concludes with a series of implications and conclusions.     

Exponential random graph models for multilevel networks

Modern multilevel analysis, whereby outcomes of individuals within groups take into account group membership, has been accompanied by impressive theoretical development (e.g. Kozlowski and Klein, 2000) and sophisticated methodology (e.g. Snijders and Bosker, 2012). But typically the approach assumes that links between groups are non-existent, and interdependence among the individuals derives solely from common group membership. It is not plausible that such groups have no internal structure nor they have no links between each other. Networks provide a more complex representation of interdependence. Drawing on a small but crucial body of existing work, we present a general formulation of a multilevel network structure. We extend exponential random graph models (ERGMs) to multilevel networks, and investigate the properties of the proposed models using simulations which show that even very simple meso effects can create structure at one or both levels. We use an empirical example of a collaboration network about French cancer research elites and their affiliations (0125 and 0120) to demonstrate that a full understanding of the network structure requires the cross-level parameters. We see these as the first steps in a full elaboration for general multilevel network analysis using ERGMs.     

Referrals, language proficiency, and enrolment for children's mental health services

Alberta Health Services maintains a database of children, adolescents and adults referred to the child and adolescent mental health and psychiatry intake service. In this study, we sought to systematically assess the impact, if any, of English language proficiency on enrolment of children for mental health services. Specifically, we assessed the extent to which children referred for mental health services were enrolled. In doing so, we categorized our sample (12,143) as English Proficient (EP), or Less English Proficient (LEP). Overall, we found that LEP children were significantly less likely to be enrolled compared to EP children. This disparity in enrolment was only present when other variables were not taken into account. English Proficiency is an important factor for some subgroups.     

Attitudes towards and perception of gambling among secondary school students in a developing country

ABSTRACT

Gambling is common in Nigeria and over the years has gained wide acceptability among the populace. Improved technology and legalization of gambling have led to increased gambling opportunities among young people. The aim of this study is to determine the attitude towards and perception of gambling among a sample of secondary school students in South East Nigeria. A total of 507 male students from three male-only urban Secondary Schools in Owerri, Imo State participated in the study. Multistage sampling technique was used in sample selection. Data was collected using a self-administered socio-demographic questionnaire and the 9 Item Attitude Towards Gambling Scale. Results showed an overall negative perception of gambling. Majority of the respondents (82.8%) perceived gambling as a risky activity while few (27.3%) perceived it as a good way of earning an income quickly. More than half of the respondents (52.7%) believed that gambling yields a high return. There was a significant association between parental gambling and positive attitude towards gambling (X = 6.27, p = 0.04). Thus, preventive strategies targeted towards changing gambling attitudes in parents may serve a dual role of changing attitudes and perception of gambling in their offspring.     

Managing Organizational Culture: Compliance or Genuine Change?

The issue of managing culture is of key importance within management theory and practice. A number of extant studies have found that attempts to 'manage' culture frequently degenerate into the enforcement of espoused behaviours. The objective of this paper is to provide empirical evidence and discussion of the consequences of management attempts to change culture. The paper reviews existing theory pertaining to organizational culture change and presents the desire to control as the rationale for management attempts to modify culture. After a brief discussion of the research design and methodology employed, the findings of a single case study are presented. The findings suggest that within the case study organization, a recent change initiative had resulted in changes to material manifestations, behaviours and in some cases values. However, it is noted that modifications to values could be the result of 'instrumental value compliance'. The paper culminates with conclusions, implications and suggestions for further research.