Blinded continuous monitoring in clinical trials with recurrent event endpoints

In studies with recurrent event endpoints, misspecified assumptions of event rates or dispersion can lead to underpowered trials or overexposure of patients. Specification of overdispersion is often a particular problem as it is usually not reported in clinical trial publications. Changing event rates over the years have been described for some diseases, adding to the uncertainty in planning. To mitigate the risks of inadequate sample sizes, internal pilot study designs have been proposed with a preference for blinded sample size reestimation procedures, as they generally do not affect the type I error rate and maintain trial integrity. Blinded sample size reestimation procedures are available for trials with recurrent events as endpoints. However, the variance in the reestimated sample size can be considerable in particular with early sample size reviews. Motivated by a randomized controlled trial in paediatric multiple sclerosis, a rare neurological condition in children, we apply the concept of blinded continuous monitoring of information, which is known to reduce the variance in the resulting sample size. Assuming negative binomial distributions for the counts of recurrent relapses, we derive information criteria and propose blinded continuous monitoring procedures. The operating characteristics of these are assessed in Monte Carlo trial simulations demonstrating favourable properties with regard to type I error rate, power, and stopping time, ie, sample size.     

Changing paradigms of development in an evolutionary perspective

The paper gives an assessment of the theoretical foundations of development planning laid in the 1950s and 1960s, and the conceptual shifts since the turbulent 1970s questioning previous patterns of macroeconomic regulation. The call today is for management styles suited to cope with evolutionary processes. Their crucial elements in the face of overall change are sensitive early diagnosis, flexible adjustment, continuous individual and social learning, the building of technological potential, and self-organization. There is an emerging search for an evolutionary ethics accepting responsibility for the further continuation of life on the planet in view of ecological constraints and recognizing basic principles of evolution such as openness, non-equilibrium, and the positive role of fluctuations in reaching higher levels of complexity and order. Value systems have an ever more explicit impact on the direction of social change.     

Diagnosis and therapy of male gamblers in a university psychiatric hospital

From 1980 to mid-1990 fifty-one gamblers were evaluated and treated at the psychiatric university hospital of Homburg/Saar in Germany. All were men with a mean age of 33.7 years. Gambling had lasted 5.2 years on average. Most patients were motivated to undergo therapy by members of their family. The majority of them had been in psychotherapeutic treatment before. Thirty-six of the 51 patients had committed punishable acts including fraud and embezzlement and, in 7 cases, robbery. The sample could be divided into three clinical subgroups. The first group consisted of patients with severe psychiatric diseases such as schizophrenia, manic-depressive illness or organic brain disorder. Patients of the second group suffered from serious personality disorders. Those of the third group showed deep-rooted problems in their current relationships.This article is an extension of the special issue on Gambling in Europe edited by Iver Hand, M.D.     

The surprising effectiveness of earliest operation due-date sequencing

In make-to order production, schedule reliability is very important but still not sufficiently accomplished in industrial practice by the vast majority of companies. It has been known for long that processing the orders at a workstation in the order of their operation due-dates can compensate for lateness in the arrival at the workstation within certain boundaries. The paper analyses the effectiveness of earliest operation due date (EODD) sequencing by comparing it to an optimistic theoretical boundary. The surprising result is that EODD can nearly fully exploit the theoretical potential. It should therefore be used in practice whenever schedule reliability is important, with only few exceptions. Its effectiveness though is increasing with the workstation’s WIP level and thus is in conflict with the objective to reduce WIP levels and throughput times. A simple forecasting model allows to assess the extent to which lateness can be compensated by EODD sequencing and which schedule compliance can be achieved.     

Integrative Entrepreneurship-Forschung — Identifikation von Schnittstellen zwischen soziologischer und ökonomischer Perspektive

In this paper three prominent discourses of Entrepreneurship Research — 1) the Entrepreneur as an actor in society, 2) the embeddedness of the research object of Entrepreneurship Research and 3) the determinants of entrepreneurship processes — are analyzed for possible interfaces between a sociological and economical perspective. This analyses results in a systemized portfolio of research topics, which seem to be especially attractive for such an integrative research approach. The results of a survey of 105 entrepreneurship researchers in the German speaking world underpin the relevance of the identified interfaces and allow for their priorization. That way we contribute to an integration of this field as the presented set of identified interfaces, in a first step, provides a feasible agenda for interdisciplinary (empirical) follow-up research whose results — in a second step — can build elements of an integrative concept of Entrepreneurship Research.     

Estimating German overqualification with stochastic earnings frontiers

We estimate individual potential income with stochastic earnings frontiers to measure overqualification as the ratio between actual income and potential income. To do this, we remove a drawback of the IAB employment sample, the censoring of the income data, by multiple imputation. The measurement of overqualification by the income ratio is also a valuable addition to the overeducation literature because the well-established objective or subjective overeducation measures focus on some ordinal matching aspects and ignore the metric income and efficiency aspects of overqualification.