Testing the stability of a linear dynamic model

In this paper we present a Wald or distance test for testing the stability of a linear dynamic model. Stability requires that all latent roots of the system simultaneously satisfy inequality restrictions. Unlike previous tests proposed in the literature our procedure is capable of testing the restrictions simultaneously. Therefore, the test asymptotically has the correct size. The procedure can be applied in practice if stability is not a requirement for identification of the dynamic model.     

Efficiency gains due to using missing data procedures in regression models

The problem of missing observations in regression models is often solved by using imputed values to complete the sample. As an alternative for static models, it has been suggested to limit the analysis to the periods or units for which all relevant variables are observed. The choice of an imputation procedure affects the asymptotic efficiency of the method used to subsequently estimate the parameters of the model. In this note, we show that the relative asymptotic efficiency of three estimators designed to handle incomplete samples depends on parameters that have a straightforward statistical interpretation. In terms of a gain of asymptotic efficiency, the use of these estimators is equivalent to the observation of a percentage of the values which are actually missing. This percentage depends on three R²-measures only, which can be straightforwardly computed in applied work. Therefore it should be easy in practice to check whether it is worthwhile to use a more elaborate estimator.     

Network constraints on social action: preliminaries for a network theory

The network approach to social reality lacks a theoretical body that backs up the assumption of the working of structural rules. This contribution is an attempt toward investigation of the possibility of a theory of the effects of network properties on social action. The structure and effects of social networks vary along with the aims put forward in the relations of which they are composed. Considering those aims, three different sorts of networks can be distinguished — sentiment-, interest- and power-networks — involving distinct action logics. When the nature of the ties is known, predictions about the structure of the resulting social networks, type of social control and type of exchange taking place within them, can be made.     

Development of an instrument for assessing workstyle in checkout cashier work (BAsIK)

Checkout cashier work consists of handling a large number of items during a work shift, which implies repetitive movements of the shoulders, arms and hands/wrists, and a high work rate. The work is associated with a high prevalence of disorders in the neck and upper extremity. The concept of workstyle explains how ergonomic and psychosocial factors interact in the development of work-related upper extremity disorders. The aim of the project was to develop an instrument for the occupational health services to be used in the efforts to prevent upper extremity disorders in checkout cashier work. The instrument is based on the workstyle concept and is intended to be used as a tool to identify high-risk workstyle and needs for interventions, such as training and education. The instrument, BAsIK, consists of four parts; a questionnaire about workstyle, an observation protocol for work technique, a checklist about the design of the checkout and a questionnaire about work organization. The instrument was developed by selecting workstyle items developed for office work and adapting them to checkout cashier work, discussions with researchers and ergonomists, focus-group interviews with cashiers, observations of video recordings of cashiers, and studies of existing guidelines and checklists.     

Project Scheduling—Theory and Practice

The project scheduling problem involves the scheduling of project activities subject to precedence and/or resource constraints. Of obvious practical importance, it has been the subject of intensive research since the late fifties. A wide variety of commercialized project management software packages have been put to practical use. Despite all these efforts, numerous reports reveal that many projects escalate in time and budget and that many project scheduling procedures have not yet found their way to practical use. The objective of this paper is to confront project scheduling theory with project scheduling practice. We provide a generic hierarchical project planning and control framework that serves to position the various project planning procedures and discuss important research opportunities, the exploration of which may help to close the theory‐practice gap.     

Forbidden Fruit? A Longitudinal Study of Christianity,Sex, and Marriage

Does religion still play a role in explorations of romance and sexuality among adolescents and young adults in a secular society such as Norway? Does it influence the type of living arrangements chosen? A population-based sample (n = 2,454) was followed longitudinally from their midteens to their late 20s using survey and register data. Christian involvement in teenage years was associated with subsequent less “precoital” exploration, less masturbation, delayed sexual intercourse, and a smaller number of sex partners. However, there were no associations with prevalence of same-sex experiences. Christians also postponed initiating romantic relationships and chose marriage over cohabitation. Associations were reduced after controlling for confounding factors but remained significant. Some associations (for example, the form of residential union chosen) were present only in the most “active” Christians. In other areas, such as “precoital explorations” and the age at which intercourse is initiated, Christian norms seem to play a role in much broader segments of the population. The findings indicate that Christianity may continue to influence young Norwegians’ experiences of sexuality and cohabitation more than has been expected.