Auf der Suche nach der Wunsch-Universität — im Stich gelassen

Hochschulrankings beanspruchen, (angehenden) Studierenden Orientierungshilfe bei der Suche nach der für sie besten Universit?t zu geben. Wir kritisieren diesen Anspruch aus zwei Perspektiven: Erstens k?nnen Indikatoren der Art, wie sie den am meisten verbreiteten Rankings zu Grunde liegen, nur sehr begrenzt Auskunft darüber geben, was Studierende mit unterschiedlichen Interessen und Ansprüchen an das Studium an den Universit?ten eigentlich erwartet. Zweitens besteht zwischen den Rankings teilweise so wenig übereinstimmung, dass auch in dieser Hinsicht die beanspruchte Orientierungsfunktion ?u?erst zweifelhaft erscheint. Studierenden w?re mit detaillierten Informationen über die Spezifika der jeweiligen Universit?ten und der einzelnen Studieng?nge gerade in der gegenw?rtigen Umbruchsituation an den deutschen Hochschulen weitaus mehr geholfen.     

Distance-based variable generation with applications to the FACT experiment

We introduce a new way to construct variables for classification in a setting of astronomy. The newly constructed variables complement the currently used Hillas parameters and are specifically designed to improve the classification. They are based on fitting elliptic or skewed bivariate distributions to images gathered by imaging atmospheric Cherenkov telescopes and evaluating the distance between the observed and the fitted distribution. As distance measures we use the Chi-square distance, the Kullback–Leibler divergence and the Hellinger distance. The new variables lead to an improved classification in terms of misclassification errors.     

Collingridge’s dilemma and technoscience

Collingridge’s dilemma is one of the most well-established paradigms presenting a challenge to Technology Assessment (TA). This paper aims to reconstruct the dilemma from an analytic perspective and explicates three assumptions underlying the dilemma: the temporal, knowledge and power/actor assumptions. In the light of the recent transformation of the science, technology and innovation system—in the age of “technoscience”—these underlying assumptions are called into question. The same result is obtained from a normative angle by Collingridge himself; he criticises the dilemma and advances concepts on how to keep a technology controllable. This paper stresses the relevance of the dilemma and of Collingridge’s own ideas on how to deal with the dilemma. Today, a positive interpretation of technoscience for effective TA is possible.     

Statistical inference of the efficient frontier for dependent asset returns

In the paper we consider the three characteristics of the efficient frontier. These characteristics are estimated by substituting the unknown parameters by the sample counterparts. Assuming that the asset returns follow a stationary Gaussian process it is shown that the estimated characteristics are asymptotically normally distributed. This result is used to determine the joint asymptotic distribution of the estimated portfolio return and the estimated portfolio variance in the case of the expected utility portfolio and the tangency portfolio, respectively.     

The influence of parameter estimation on the ARL of Shewhart type charts for time series

In this paper we discuss the behavior of the Shewhart residual chart and the modified Shewhart chart if the parameters of the underlying process are unknown and thus have to be estimated. We focus on the estimation of the variance. For AR models we also consider the estimation of the AR coefficients. The average run length (ARL) of the control chart with estimated parameters is compared with the ARL of the scheme for known parameters and with the ARL for independent variables. Additionally, we give recommendations on the choice of the estimators in the context of Shewhart control schemes.     

Dynamic semiparametric factor models in risk neutral density estimation

Dynamic semiparametric factor models (DSFM) simultaneously smooth in space and are parametric in time, approximating complex dynamic structures by time invariant basis functions and low dimensional time series. In contrast to traditional dimension reduction techniques, DSFM allows the access of the dynamics embedded in high dimensional data through the lower dimensional time series. In this paper, we study the time behavior of risk assessments from investors facing random financial payoffs. We use DSFM to estimate risk neutral densities from a dataset of option prices on the German stock index DAX. The dynamics and term structure of risk neutral densities are investigated by Vector Autoregressive (VAR) methods applied on the estimated lower dimensional time series.     

Modularity in philosophy, the neurosciences, and psychiatry

The neurosciences are generating new findings regarding genetic and neurobiological aspects of the pathophysiology of mental disorders. Especially, certain genetic risk factors like neuregulin-1 seem to predispose individuals to a psychotic phenotype beyond the limits of traditional classificatory boundaries between organic psychoses in Alzheimer’s disease, bipolar affective disorder and schizophrenia. Little, however, is known about how such genetic risk factors actually confer an increased risk for psychosis in an individual patient. A gap between neuroscientific findings and psychopathological phenomena exists. The main hypothesis how this gap may be bridged is that mental disorders arise as a consequence of dysfunctions of normal mental functions. Modularity may provide a useful conceptual framework in that temporally and/or spatially stable neural circuits subserve certain physiological functions of the human brain, which become the target of pathophysiological effectors. The idea of a modular construction of the human brain is based on neurobiological evidence regarding the columnar architecture of the cerebral cortex, which provides certain elementary analytical functions. Modular dysfunctions may be assessed with methods of experimental psychopathology, in which subsystems of brain functions are tested with standardized experimental psychological techniques (functional psychopathology). The main questions here are how to define a module, and whether the classical neuroscientific definitions can be used to characterize higher integrative functions of the human brain.     

Simulation experiments of resource-allocation decisions in two-level organizations

A model two-level organization consisting of headquarters and two divisions is considered. Headquarters is faced with a decision-problem: to allocate certain scarce resources in a “good” way between the two divisions. Three different methods that can be used to reach that allocation decision are studied. Those three methods are (1) to simply divide the resources equally between the divisions; (2) a method based on an iterative pricing mechanism; and (3) an adaptation of the Dantizig-Wolfe decomposition algorithm. The paper investigates, by means of a set of simulation experiments, the effects of these methods on organizational performance, both as regards overall payoff and divisional payoff. With respect to divisional payoff, a divisional payoff-structure is postulated, and it is examined whether divisional payoff can be improved through “cheating.”     

The Contribution of Assisted Reproduction to Completed Fertility: An Analysis of Danish Data

Assisted reproduction has a minor but increasing influence on childbearing trends in advanced societies. In Denmark, the use of assisted reproduction technology (ART) has become particularly widespread. At the same time, Danish women born in the late 1950s and the 1960s experienced stabilization or even a slight increase in their mean number of children. Broad availability and widespread use of assisted reproduction may become important factors contributing to maintaining relatively high completed fertility among the younger cohorts of Danish women. To explore this idea, we analyze and project cohort trends in fertility rates among native Danish women born in 1960‐78 and examine the likely contribution of assisted reproduction to these trends. The projected proportion of children born after ART treatment shows a substantial increase from 2.1 percent among women born in 1965 to 4‐5 percent among women born in 1978, with an estimated net impact of ART (as compared with the hypothetical situation where no ART treatment was available) on the order of 3‐4 percent. When intrauterine inseminations are included, this implies that up to 7 percent of children of those native Danish women born in 1975 and later will likely be conceived by infertility treatment.