Bootstrapping regression models with BLUS residuals

To bootstrap a regression problem, pairs of response and explanatory variables or residuals can be resam‐pled, according to whether we believe that the explanatory variables are random or fixed. In the latter case, different residuals have been proposed in the literature, including the ordinary residuals (Efron 1979), standardized residuals (Bickel & Freedman 1983) and Studentized residuals (Weber 1984). Freedman (1981) has shown that the bootstrap from ordinary residuals is asymptotically valid when the number of cases increases and the number of variables is fixed. Bickel & Freedman (1983) have shown the asymptotic validity for ordinary residuals when the number of variables and the number of cases both increase, provided that the ratio of the two converges to zero at an appropriate rate. In this paper, the authors introduce the use of BLUS (Best Linear Unbiased with Scalar covariance matrix) residuals in bootstrapping regression models. The main advantage of the BLUS residuals, introduced in Theil (1965), is that they are uncorrelated. The main disadvantage is that only n —p residuals can be computed for a regression problem with n cases and p variables. The asymptotic results of Freedman (1981) and Bickel & Freedman (1983) for the ordinary (and standardized) residuals are generalized to the BLUS residuals. A small simulation study shows that even though only n — p residuals are available, in small samples bootstrapping BLUS residuals can be as good as, and sometimes better than, bootstrapping from standardized or Studentized residuals.     

Correlation in a Bayesian framework

The authors consider the correlation between two arbitrary functions of the data and a parameter when the parameter is regarded as a random variable with given prior distribution. They show how to compute such a correlation and use closed form expressions to assess the dependence between parameters and various classical or robust estimators thereof, as well as between p‐values and posterior probabilities of the null hypothesis in the one‐sided testing problem. Other applications involve the Dirichlet process and stationary Gaussian processes. Using this approach, the authors also derive a general nonparametric upper bound on Bayes risks.     

Estimation of geodesic tortuosity and constrictivity in stationary random closed sets

We investigate the problem of estimating geodesic tortuosity and constrictivity as two structural characteristics of stationary random closed sets. They are of central importance for the analysis of effective transport properties in porous or composite materials. Loosely speaking, geodesic tortuosity measures the windedness of paths, whereas the notion of constrictivity captures the appearance of bottlenecks resulting from narrow passages within a given materials phase. We first provide mathematically precise definitions of these quantities and introduce appropriate estimators. Then, we show strong consistency of these estimators for unboundedly growing sampling windows. In order to apply our estimators to real data sets, the extent of edge effects needs to be controlled. This is illustrated using a model for a multiphase material that is incorporated in solid oxide fuel cells.     

We are not in control—embrace uncertainty and trust in what emerges. Peter Senge on the legacy and future of Change Management

Gruppe. Interaktion. Organisation. Zeitschrift für Angewandte Organisationspsychologie (GIO) - Peter Senge is a senior lecturer at the MIT Sloan School of Management and founder of...     

The Shifting Meanings of Popular Engagement in Swedish Society

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - The aim of this article is to contribute to the Swedish debate on popular engagement by studying changes in popular...     

L'effet des obstacles aux échanges sur l'emploi généré par les chaînes d'approvisionnement mondiales

Les auteurs étudient l'effet des obstacles aux échanges internationaux de biens et de services sur les marchés du travail des pays producteurs en partant des estimations du BIT sur l'emploi imputable aux chaînes d'approvisionnement mondiales. L'analyse empirique confirme largement les prédictions d'un modèle théorique calibré avec des données de la base WIOD (2000 et 2011). Les obstacles au commerce de produits manufacturés ou de services ont un effet transfrontalier, intrasectoriel et intersectoriel, sur l'emploi, qui reflète l'interdépendance croissante entre pays et secteurs. L'effet intersectoriel s'affirme avec le temps. Les politiques commerciales semblent donc pouvoir avoir des effets externes importants sur les marchés du travail étrangers.     

Psychological Vulnerability and Problem Gambling: The Mediational Role of Cognitive Distortions

Despite numerous studies demonstrating the influence of cognitive distortions on gambling problem severity, empirical data regarding the role of psychological vulnerability on the latter is limited. Hence, this study assesses the mediating effect of cognitive distortions between psychological vulnerability (personality and mood), and gambling problem severity. It also verifies whether the relationships between these variables differs according to the preferred gambling activity. The sample is composed of 272 male gamblers [191 poker players; 81 video lottery terminal (VLT) players] aged between 18 and 82 years (M = 35.2). Bootstrap analysis results revealed that cognitive distortions mediate the effect of narcissism on gambling problem severity for both groups. The level of depression for VLT players significantly predicted gambling problem severity, both directly and indirectly via the mediating effect of cognitive distortions. Mediation analyses also indicated that narcissism had an indirect impact on problem gambling through cognitive distortions for both groups. These findings suggest that certain vulnerabilities related to personality and mood may influence cognitive distortion intensity and gambling problem severity. In addition, psychological vulnerabilities could differ based on preferred gambling activity. These results may be useful for prevention policies, identifying high risk gamblers and planning psychological interventions.     

Self-Directed Gambling Changes: Trajectory of Problem Gambling Severity in Absence of Treatment

Most problem gamblers do not seek formal treatment, recovering on their own through cognitive re-appraisal or self-help strategies. Although barriers to treatment have been extensively studied, there is a paucity of research on self-directed changes in problem gambling and very few studies have examined these changes prospectively. The aim of this study was to examine the trajectory of gambling severity and behavior change over an 18-month period, among a sample of non-treatment seeking/attending problem gamblers recruited from the community (N?=?204) interested in quitting or reducing gambling. Separate mixed effects models revealed that in absence of formal treatment, significant reductions in gambling severity, frequency, and amount gambled could be observed over the course of a 6 to 9-month period and that changes experienced within the first 12 months were maintained for an extended 6 months. Problem gambling severity at baseline was significantly associated with changes in severity over time, such that participants with more severe gambling problems demonstrated greater reductions in their gambling severity over time. A total of 11.1% of participants gambled within a low-risk threshold at 18 months, although 28.7% of the sample reported consecutive gambling severity scores below problem levels for the duration of 1 year or longer. The findings suggest that among problem gamblers motivated to quit or reduce their gambling, significant self-directed changes in gambling severity can occur over a relatively short time. Additional prospective studies are needed to document the role of specific self-help tools or thought processes in exacting gambling changes.     

Nah der Wissenschaft und fern der Führung in einer Fach‑/Expertenlaufbahn?

In order to motivate and retain technical employees, representatives of strategic career management face the challenge of establishing alternative career paths in addition to the common leadership/management career. Surveying a sample of 629 doctorate holders from the STEM fields, we differentiated between five career paths within and beyond structured career models. Structured career ladders were predominantly present in major enterprises. Female participants less frequently reported to be part of a structured career path. Entering a leadership/management career seems to occur at a later stage compared to other paths. Generally, advancement on a leadership/management path was related to stronger increases in incentives than climbing up the technical/expert or project management ladders. Contrary to our expectations, we did not find members of a technical/expert career to work closer to basic research and their initial qualification than their colleagues on other career paths. Members of leadership/management paths reported to have significantly more leadership responsibility than those working on alternative paths.