An alternative competing risk model to the Weibull distribution for modelling aging in lifetime data analysis

A simple competing risk distribution as a possible alternative to the Weibull distribution in lifetime analysis is proposed. This distribution corresponds to the minimum between exponential and Weibull distributions. Our motivation is to take account of both accidental and aging failures in lifetime data analysis. First, the main characteristics of this distribution are presented. Then, the estimation of its parameters are considered through maximum likelihood and Bayesian inference. In particular, the existence of a unique consistent root of the likelihood equations is proved. Decision tests to choose between an exponential, Weibull and this competing risk distribution are presented. And this alternative model is compared to the Weibull model from numerical experiments on both real and simulated data sets, especially in an industrial context.     

Evaluation of and support for group prototypical leaders: a meta-analysis of twenty years of empirical research

The key premise of the social identity theory of leadership, that group prototypical leaders are more favorably evaluated than less prototypical leaders, is supported by twenty years of research. To establish overall how much variance in leader evaluation is attributable to leader prototypicality we conducted a meta-analysis of 35 independent studies (N = 6678). Prototypicality accounted for 24% of variance in leader evaluation. There was a large overall effect (r = .49), which was moderated by research method and type of evaluation. The relationship was stronger in correlational studies (r = .60) than experiments (r = .35), and on measures of leader trust (r = .63) than effectiveness (r = .43). Theoretical implications and future directions are discussed.     

The Sexual Health of Transgender Men: A Scoping Review

There is a general paucity of research concerning the sexual health of transgender individuals, and most existing research focuses on transgender women. A scoping review concerning the sexual health of transgender men was conducted to identify gaps in the literature and to highlight opportunities for future research and intervention. A comprehensive search of seven databases was conducted. The Joanna Briggs Institute Reviewers’ Manual was used as a framework. Some 7,485 articles were initially identified using a search strategy applied to seven online databases: 54 articles were identified as relevant to the research questions and reviewed in detail; of those, 33 were included in the final analysis. Studies were conceptualized into four broad themes: sexual behaviors, sexual identity, sexual pleasure and sexual function, and transactional sex. Besides an overall lack of research, existing studies were often characterized by small convenience samples that do not allow for generalization to the larger population of transgender men. Significant gaps in the literature regarding sexual coercion, sexual and intimate partner violence, and relationship quality and functioning among transgender men exist. There is a need to improve the scope and depth of research examining the sexual health of this population, especially concerning sexual risk behaviors and structural barriers to sexual health care access.     

Adaptive nonparametric estimation in the presence of dependence

We consider nonparametric estimation problems in the presence of dependent data, notably nonparametric regression with random design and nonparametric density estimation. The proposed estimation procedure is based on a dimension reduction. The minimax optimal rate of convergence of the estimator is derived assuming a sufficiently weak dependence characterised by fast decreasing mixing coefficients. We illustrate these results by considering classical smoothness assumptions. However, the proposed estimator requires an optimal choice of a dimension parameter depending on certain characteristics of the function of interest, which are not known in practice. The main issue addressed in our work is an adaptive choice of this dimension parameter combining model selection and Lepski's method. It is inspired by the recent work of Goldenshluger and Lepski [(2011), ‘Bandwidth Selection in Kernel Density Estimation: Oracle Inequalities and Adaptive Minimax Optimality’, The Annals of Statistics, 39, 1608–1632]. We show that this data-driven estimator can attain the lower risk bound up to a constant provided a fast decay of the mixing coefficients.     

Penalized multidimensional fitting for protein movement detection

The three-dimensional structure of a given protein can take different conformations depending upon the reaction it undergoes and its substrate/cofactor/partners binding state. Various methods exist to study these conformational changes but only one, called DynDom, is clearly focused on movement detection. An alternative method is proposed, making use of multivariate data analysis, called ‘penalized Multidimensional Fitting (penalized MDF)’ based on penalized movements of points in order to approach the distances between points after movement to the distances given by the reference matrix. The objective is to detect the amino acids that undergo an important movement by fitting the distances of one conformation to the distances of the second one by modifying only the coordinates of the first one. This method is applied to three different proteins.     

Entrer aux Chantiers : les transformations de la socialisation professionnelle et des rapports intergénérationnels aux Chantiers de l’Atlantique (1950–2005)

Based on the data of a sociological study conducted among three generations of workers of Chantiers de l’Atlantique, this article describes and analyzes, in a dynamic prospect, first, the changes in employment and labor in the shipbuilding industry over the last five decades (1950–2005) and, secondly, the changes in professional socialization and intergenerational relationships at work in the group of the metal-workers. On the basis of the postulate according to which the age and the generation are not sociological data in themselves but result from a singular social construction, our purpose is to show how the mode of production of the three working generations observed is directly related to differences in access to employment on the one hand, and to professional and organizational socialization on the other hand.     

“Wrong place to get help”: A field experiment on luxury stores and helping behavior

Three experiments were conducted in field settings. It was hypothesized that luxury stores may act as environmental reminders of materialism and that helpfulness would vary according to the presence or absence of such cues. Study 1 (N = 80) indicated that consumers coming out of famous brand stores displayed less helpfulness, as compared to mere passersby. Study 2 (N = 112) showed passersby were less helpful near a luxury brand store than in an ordinary street with no shops. In Study 3 (N = 360), passersby were less helpful when walking down a street lined with highly exclusive stores, as compared to streets with ordinary stores or no stores. Results, limitations, and directions for future research are discussed.     

LIFE AFTER DEBT: POSTGRADUATION CONSEQUENCES OF FEDERAL STUDENT LOANS

We estimate the causal effect of student loans on postgraduation labor market outcomes exploiting a kink in the formula determining eligibility for need‐based student loans. Using a representative sample of students graduating with a bachelor's degree in 1993, we find that student debt has nonnegative effects on earnings. This result holds with differing levels of statistical significance across a battery of different empirical designs: (1) ordinary least squares, (2) partially linear, and (3) regression kink. We find similar results for the 2008 graduating cohort. (JEL I22, I26, J32, J33)