On multiple constraint skewed models

The Azzalini [A. Azzalini, A class of distributions which includes the normal ones, Scandi. J. Statist. 12 (1985), pp. 171–178.] skew normal model can be viewed as one involving normal components subject to a single linear constraint. As a natural extension of this model, we discuss skewed models involving multiple linear and nonlinear constraints and possibly non-normal components. Particular attention is devoted to a distribution called the extended two-piece normal (ETN) distribution. This model is a two-constraint extension of the two-piece normal model introduced by Kim [H.J. Kim, On a class of two-piece skew normal distributions, Statistics 39(6) (2005), pp. 537–553.]. Likelihood inference for the ETN distribution is developed and illustrated using two data sets.     

Bootstrap and permutation rank tests for proportional hazards under right censoring

We address the testing problem of proportional hazards in the two-sample survival setting allowing right censoring, i.e., we check whether the famous Cox model is underlying. Although there are many test proposals for this problem, only a few papers suggest how to improve the performance for small sample sizes. In this paper, we do exactly this by carrying out our test as a permutation as well as a wild bootstrap test. The asymptotic properties of our test, namely asymptotic exactness under the null and consistency, can be transferred to both resampling versions. Various simulations for small sample sizes reveal an actual improvement of the empirical size and a reasonable power performance when using the resampling versions. Moreover, the resampling tests perform better than the existing tests of Gill and Schumacher and Grambsch and Therneau . The tests’ practical applicability is illustrated by discussing real data examples.

     

Has Successful Terror Gone to Ground?

This article considers all 87 attacks worldwide against air and rail transport systems that killed at least two passengers over the 30‐year period of 1982–2011. The data offer strong and statistically significant evidence that successful acts of terror have “gone to ground” in recent years: attacks against aviation were concentrated early in the three decades studied whereas those against rail were concentrated later. Recent data are used to make estimates of absolute and comparative risk for frequent flyers and subway/rail commuters. Point estimates in the “status quo” case imply that mortality risk from successful acts of terror was very low on both modes of transportation and that, whereas risk per trip is higher for air travelers than subway/rail commuters, the rail commuters experience greater risk per year than the frequent flyers.     

Early Transition Stages and Heterogeneity in Criminal Careers among Young Offenders*

Dans cet article, nous examinons différents modèles de rapports avec les forces policières parmi des sous-populations hétérogènes de jeunes, dans les premiers stades de transition de leur carrière criminelle. Nous croyons que la recherche axée sur l'hétérogénéité et sur les premiers stades de la transition vers la criminalité peut nous renseigner sur les éléments de la dynamique comportementale - jusqu'ici ignorés - dans l'étude de l'apparition d'un comportement criminel et de sa persistance. À partir de données policières informatisées provenant d'une grande ville de l'ouest du Canada, nous utilisons certains modèles de survie basés sur des événements pour dégager des modèles d'apparition et de persistance de comportements criminels sur une période de six mois, dans les premiers rapports avec la police. Les résultats démontrent des modifications importantes à court terme dans le comportement criminel de sousgroupes de jeunes de niveaux différents. Certains semblent avoir un comportement criminel ponctuel, qu'ils abandonnent par la suite, tandis que d'autres continuent de se comporter en criminels, en augmentant la fréquence et le taux d'infractions. Toutefois, certains modèles hétérogènes existent au sein de ces sous-groupes de jeunes délin quants dans les premières phases de développement de la criminalité. We investigate distinctive patterns of police contacts among heterogeneous subpopulations of youths in the early transition stages of their criminal careers. We argue that research focussing upon heterogeneity and the initial transition stages of criminality can provide insights into behavioural dynamics previously overlooked in the study of the onset and development of criminal careers. Using computerized police archival data from a large western Canadian city, we employ event history survival models to estimate patterns of onset and persistence for delinquent careers over six-month intervals in the early stages of police contact. Our results provide strong evidence of meaningful short-term change in offending among multiple levels of youth subgroups. Some youths appear to offend only briefly and then desist, while others continue offending and at a higher rate. However, there also appear to be patterns of heterogeneity within as well as between these subgroups of young offenders during the early stages of criminal careers.     

A model of religion and death

This paper provides a rationale for several empirical findings regarding religion. The main one is between religion and the fear of death. Some empirical evidence indicates moderately religious individuals fear death more than either atheists or extremely religious individuals. The model also explains the positive relationship often found between religious activity (e.g. church attendance) and age. It also provides an explanation of the positive relationship between education and religious activity despite a negative relationship between education and religious belief.     

On the Exact and Near-Exact Distributions of the Product of Generalized Gamma Random Variables and the Generalized Variance

In this article, the authors first obtain the exact distribution of the logarithm of the product of independent generalized Gamma r.v.’s (random variables) in the form of a Generalized Integer Gamma distribution of infinite depth, where all the rate and shape parameters are well identified. Then, by a routine transformation, simple and manageable expressions for the exact distribution of the product of independent generalized Gamma r.v.’s are derived. The method used also enables us to obtain quite easily very accurate, manageable and simple near-exact distributions in the form of Generalized Near-Integer Gamma distributions. Numerical studies are carried out to assess the precision of different approximations to the exact distribution and they show the high accuracy of the approximations provided by the near-exact distributions. As particular cases of the exact distributions obtained we have the distribution of the product of independent Gamma, Weibull, Frechet, Maxwell-Boltzman, Half-Normal, Rayleigh, and Exponential distributions, as well as the exact distribution of the generalized variance, the exact distribution of discriminants or Vandermonde determinants and the exact distribution of any linear combination of generalized Gumbel distributions, as well as yet the distribution of the product of any power of the absolute value of independent Normal r.v.’s.     

Sexual Orientation Victimization and Posttraumatic Stress Symptoms Among Lesbian,Gay, and Bisexual Youth

This cross-sectional study utilized data gathered from 350 lesbian, gay, and bisexual (LGB) youth, and examined the relationship between significant life experiences and posttraumatic stress symptoms (PSS), with an ultimate goal of analyzing contribution of sexual orientation victimization (SOV) to PSS among LGB youth. Results of bivariate analyses indicate that verbal and physical sexual orientation victimization, childhood gender atypicality, internalized homophobia, and stressful life events unrelated to sexual orientation were all individually related to PSS. Multivariate analysis showed that verbal and physical sexual orientation victimization explained a significant portion of variance, over and above the study's other variables. Internalized homophobia, stressful life events, and verbal sexual orientation victimization were found to be the most significant predictors of PSS among LGB youth.     

The Influence of Perceived Supervisor Listening Behavior on Employee Commitment

This study seeks to examine the influence of perceived supervisor listening on employee commitment in an organization. Research suggests that in today's organizations managers spend the largest percentage of their time listening, followed by speaking, reading, and writing. Although training addresses speaking and public presentations, interpreting technical reports, and instruction in technical writing, little has been done to either research or train listening skills.

Listening research has primarily focused on listening measurements and assessment (see Rhodes, Watson & Barker, 1990), and identification of specific behaviors associated with listening (see Lobdell & Gluc, 1990). Few studies have examined listening in the organizational setting (see Husband, Cooper, & Monsour, 1988; Husband, Schenck, & Cooper, 1988). A study by Husband, Cooper, and Monsour (1988), explored the initial question of supervisor's perceptions of their own listening behaviors in organizations. Further research by Husband, Schenck, and Cooper (1988) suggests that the subordinate's perception of supervisory listening may be different than the supervisor's actual listening behavior or the supervisor's perception of their own listening behavior. They found that subordinates did not feel at ease when communicating with their supervisors, and that the subordinates perceived that their supervisors were unwilling to listen to them.

As Husband, et al. (1988) suggests, there could be many starting points at which to address organizational listening. Based on some of the findings in their research, supervisor-subordinate listening seems to offer a logical beginning. The supervisor-subordinate relationship represents an essential link in the organizational structure (see Jablin, 1979). Given their argument, if subordinates differ in their perceptions of supervisory listening behavior, and perceive their supervisor's listening negatively, there may be a direct influence on their commitment to their jobs or the organization as a whole. This study attempts to determine the influence of perceived supervisor listening on employee commitment to the organization.

The respondents were 225 occupational employees and 53 managerial employees in a large southwestern utility company. The survey was a 69 item organizational listening questionnaire developed by Arnold (1989). The questionnaire was broken down into four dimensions: (1) feelings about the organization, (2) perception of relationship with supervisor, (3) perception of own communication behavior, and (4) organizational listening behaviors.     

Der Einfluss von Kognition und Affekt auf Unternehmensgründungsentscheidungen: Eine vergleichende Analyse von Angestellten und Unternehmern

The relationship between individuals?? entrepreneurial behavior and objective situational characteristics of an entrepreneurial opportunity??individual-opportunity nexus??lies in the focus of entrepreneurship research. The role of subjective appraisals and affective influences in the pre-entrepreneurial process was neglected in this context so far. On the basis of a questionnaire experiment with two different samples of employees and entrepreneurs, our results confirm central assumptions of cognitive appraisal and emotion theories. The subjective appraisals of objective entrepreneurial opportunities better predict entrepreneurial evaluation and exploitation decisions than the objective characteristics of the entrepreneurial opportunity. Furthermore, the results show in addition to an inverse direct effect of negative affect that the relationship between the entrepreneurial evaluation and exploitation is negatively moderated by negative affect. Our analyses indicate that the two subsamples show differences in their cognitive processes, but that they are still generally comparable. The affective influences on the pre-entrepreneurial process, however, demonstrate no group specific differences. These results extend the individual-opportunity-nexus-paradigm that is based on objective characteristics by examining the meaning of subjective appraisals and affective reactions and therefore the intersection of individuals and entrepreneurial opportunities.