The TTT transformation and a new bathtub distribution model

In this paper we use the total time on test transformation to establish a method for construction of parametric models of lifetime distributions having bathtub-shaped failure rate. We study a particular model which is simple compared to the other existing models. We derive expressions for moments and quantiles and treat estimation methods. Particularly, the maximum likelihood method is studied. Consistency proofs are given.     

A generalization of the Kaplan-Meier estimator to Harris-recurrent Markov chains

In this paper we study an extension of the Kaplan Meier estimator to the case of dependent failure times. We assume that the failure times follow a Harris recurrent Markov Chain. We prove strong convergence of the estimator and weak convergence to a Gaussian process.     

Parameter estimation for a special class of Markov chains

The followin paper is dedicated to a special class of stationary Markov chains. The transition probabilities are constructed from bivariate distribution functions of the Morgenstem-Type. These Markov chains are defined by their stationary distribution and a parameter a controlling the correlation between succeeding values of the chain. Relevant properties of the Markov chain are discussed. Some estimations of the parameter a are studied. The maximum likelihood estimator is compared with a simple estimator.     

Unemployment, life satisfaction and retrospective error

Summary.  The paper compares current and 1-year retrospective data on unemployment in the German Socio-Economic Panel study. 13% of all unemployment spells are not reported 1 year later, and another 7% are misreported. The ratio of retrospective to current unemployment has increased in recent years and is related to salience of unemployment measures such as the loss of life satisfaction that is associated with unemployment. Individuals with weak labour force attachment, e.g. women with children or individuals who are close to retirement, have the greatest propensity to under-report unemployment retrospectively. The data are consistent with evidence on retrospective bias found by cognitive psychologists and survey methodologists.     

Leadership and team identification: Exploring the followers' perspective

This study investigates the influence of leadership on followers' identification with their work group. Adopting a qualitative research approach, it takes on the followers' perspective for inductively deriving leadership behaviors that pertain to the development of team identification. Based on in-depth data from members of seven teams in the context of UN peacebuilding operations, four aggregate leadership dimensions can be identified that are conducive to members' team identification: providing guidance, encouraging involvement, role modeling, and administering teamwork. Accordingly, this study adds to the exploration of leadership behaviors relevant for team identification that have not been considered by extant research. The results may lay the foundations for future investigations on complementary effects of different leadership behaviors for fostering followers' identification with their work group.     

Evidence maps: communicating risk assessments in societal controversies: the case of engineered nanoparticles

The transparent and fair characterization of scientific evidence for reporting the results of a hazard assessment is a demanding task. In this article, we present an approach for characterizing evidence--the evidence map approach. The theoretical starting point is to view evidence characterization as a form of argumentation. Thus, evidence maps are designed to depict the evidence base, the pro and con arguments, and the remaining uncertainties, which together lead experts to their conclusions when summarizing and evaluating the scientific evidence about a potential hazard. To illustrate its use, the evidence maps approach is applied to characterizing the health-relevant effects of engineered nanoparticles. Empirical data from an online survey suggests that the use of evidence maps improves the reporting of hazard assessments. Nonexperts prefer to receive the information included in an evidence map in order to come to an informed judgment. Furthermore, the benefits and limitations of evidence maps are discussed in the light of recent literature on risk communication. Finally, the article underlines the need for further research in order to increase quality of evidence reporting.     

Synergistic effect of social support and self-efficacy on physical exercise in older adults

The purpose of the current study was to examine whether the effects of social support on physical exercise in older adults depend on individual perceptions of self-efficacy. Three hundred nine older German adults (age 65-85) were assessed at 3 points in time (3 months apart). In hierarchical-regression analyses, support received from friends and exercise self-efficacy were specified as predictors of exercise frequency while baseline exercise, sex, age, and physical functioning were controlled for. Besides main effects of self-efficacy and social support, an interaction between social support and self-efficacy emerged. People with low self-efficacy were less likely to be active in spite of having social support. People with low support were less likely to be active even if they were high in self-efficacy. This points to the importance of both social support and self-efficacy and implies that these resources could be targets of interventions to increase older adults' exercise.     

Über das asymptotische verhalten von bayesschen und maximum-likelihood-schätzungen

The paper deals with the asymptotic equivalence of the maximum-likelihood-estimator with sums of independent and identically distributed random variables for a family of distribution functions, the density of which may vanish depending on the parameter. Further the asymptotic equivalence of the maximum-likelihood-estimator with BAYES estimators is shown.