A bias analysis of Weibull models under heaped data

Retrospectively collected duration data are often reported incorrectly. An important type of such an error is heaping—respondents tend to round-off or round-up the data according to some rule of thumb. For two special cases of the Weibull model we study the behaviour of the ‘naive estimators’, which simply ignore the measurement error due to heaping, and derive closed expressions for the asymptotic bias. These results give a formal justification of empirical evidence and simulation-based findings reported in the literature. Additionally, situations where a remarkable bias has to be expected can be identified, and an exact bias correction can be performed.     

Buchbesprechungen / Book reviews

Literatur / Books

Buchbesprechungen / Book reviews     

Projection Measures And Estimation Variances Of Intensities

The paper investigates random processes of geometrical objects in Euclidean spaces. General properties of the measure of total projections are derived by means of Palm distribution. Explicit formulas for variances of the projection measure are obtained for Poisson point processes of compact sets.

Intensity estimators of fibre (surface) processes are then studied by means of projection measures. Classification of direct and indirect probes is introduced. The indirect sampling design of vertical sections and projections is generalized and its statistical properties derived.     

Job satisfaction and mental health of temporary agency workers in Europe: a systematic review and research agenda

ABSTRACT

The current systematic literature review aimed to analyse the associations between temporary agency work (TAW), job satisfaction, and mental health in Europe, as well as to outline a future research agenda. Twenty-eight scientific articles were identified by searching different data bases (i.e. PSYNDEX, PsycINFO, PubMed, and Web of Science) for the time span from January 2000 to December 2016. Our review reveals first that TAW is not consistently negatively related to job satisfaction. However, job insecurity and working conditions are important mediators in the relation of TAW and lowered job satisfaction. Second, TAW is not consistently related to all investigated types of mental health impairments. However, when focusing on specific outcomes and comparing temporary agency workers to permanent employees, we still find consistent evidence regarding higher levels of depression and fatigue among temporary agency workers. Inconsistent associations between TAW, job satisfaction and mental health can partly be attributed to unfavourable methodological aspects of the included primary studies. To address these aspects, future research should consider applying a standard measurement of TAW, including a minimum of meaningful confounding variables, improving the operationalisation of outcome variables and the study design.     

Remote control: measuring performance for value creation and governance of globally distributed knowledge work

This article examines the governance of globally distributed knowledge work. To measure performance in knowledge work, it is important to focus on what the knowledge workers do and hence view knowledge as something one does, namely the practices, instead of something one has. By following the practices of knowledge work, it was possible to evaluate the effect of measures related to organizational processes, and identify what was not well covered by the measurement tool. Strategic and long term needs such as learning and employee competence are better managed through projects. This article shows how work performance in international organizations needs two different measures: one tool for measuring short-term value creation linked to the organizational processes; and, one tool for measuring long-term value creation linked to the practices of service work made in projects. Global governance of distributed employees is therefore successfully managed through key performance measures and through understanding projects through their multiple contributions, at both an individual and an organizational level. Global long term governance needs are strategic for the entire firm. The paper rests on an in-depth empirical case study of an international professional service firm.     

Social vulnerability and migration in the wake of disaster: the case of Hurricanes Katrina and Rita

This study explores the relationship between place-based social vulnerability and post-disaster migration in the U.S. Gulf Coast region following Hurricanes Katrina and Rita. Using county-level data from the U.S. Census Bureau, we develop a regional index of social vulnerability and examine how its various dimensions are related to migration patterns in the wake of the storms. Our results show that places characterized by greater proportions of disadvantaged populations, housing damage, and, to a lesser degree, more densely built environments were significantly more likely to experience outmigration following the hurricanes. Our results also show that these relationships were not spatially random, but rather exhibited significant geographic clustering. We conclude with a discussion of the implications of these findings for future research and public policy.     

Unions and innovative activity in Germany

This study is the first attempt to investigate the influence of unions on innovative activities in Germany at the industry level. Econometric models estimated by a highly robust method and submitted to a number of specification tests indicate that trade unions do not have a negative impact on innovative activity which is measured by either the percentage of revenues spent on R&D or the percentage of employees working in R&D. This finding is consistent with evidence on the influence of unions on productivity in Germany and with considerations about the German system of industrial relations.     

Randomization of neighbour balanced generalized Youden designs

If a crossover design with more than two treatments is carryover balanced, then the usual randomization of experimental units and periods would destroy the neighbour structure of the design. As an alternative, Bailey [1985. Restricted randomization for neighbour-balanced designs. Statist. Decisions Suppl. 2, 237–248] considered randomization of experimental units and of treatment labels, which leaves the neighbour structure intact. She has shown that, if there are no carryover effects, this randomization validates the row–column model, provided the starting design is a generalized Latin square. We extend this result to generalized Youden designs where either the number of experimental units is a multiple of the number of treatments or the number of periods is equal to the number of treatments. For the situation when there are carryover effects we show for so-called totally balanced designs that the variance of the estimates of treatment differences does not change in the presence of carryover effects, while the estimated variance of this estimate becomes conservative.     

A note on testing the nullity of the between group variance in the one-way random effects model under variance heterogeneity

In an unbalanced and heteroscedastic one-way random effects model, we compare, by way of simulation, several test statistics for testing the null hypothesis that the variance of the random effects, also named the between group variance, is zero. These tests are the classical F-test, the test proposed by Jeyaratnam & Othman, the Welch test, and a modified version of Welch's test.