Effect Size Estimation and Misclassification Rate Based Variable Selection in Linear Discriminant Analysis

Supervised classifying of biological samples based on genetic information, (e.g. gene expression profiles) is an important problem in biostatistics. In order to find both accurate and interpretable classification rules variable selection is indispensable. This article explores how an assessment of the individual importance of variables (effect size estimation) can be used to perform variable selection. I review recent effect size estimation approaches in the context of linear discriminant analysis (LDA) and propose a new conceptually simple effect size estimation method which is at the same time computationally efficient. I then show how to use effect sizes to perform variable selection based on the misclassification rate which is the data independent expectation of the prediction error. Simulation studies and real data analyses illustrate that the proposed effect size estimation and variable selection methods are competitive. Particularly, they lead to both compact and interpretable feature sets.Comment: 21 pages, 2 figure

Innovation in craft enterprises - Barriers and Success Factors

The economic structure of Germany is undergoing radical changes brought about by far-reaching alterations in the global division of labour, a weakening and modification of demand trends and by the dynamics of technological and organizational innovation. These structural changes affect the craft enterprises as well. In the past craft enterprises mastered these challenges in the competition, in the market and in the technology. Moreover, the craft enterprises are responsible for many innovative products, processes and services as well as for the preservation of jobs and the creation of a large number of new jobs. The aim of our research was to find out craft enterprises which have successfully mastered these challenges within the last years. Furthermore it is important to know something about the problems enterprises had with the adjustment to the structural changes. Discovering and analysing the weaknesses is the necessary condition to remove these weaknesses and to be successful on the markets in the future. Especially innovative enterprises are expected to have competitive advantages in opposition to enterprises that are not innovative. The paper is based on an empirical survey of 133 craft enterprises in the area of the Chamber of Handicrafts Reutlingen, a mainly rural region within Baden-Wuerttemberg. The craft enterprises in this area were examined with standardized questionnaires and interviews. The main focus in our survey was placed on variables, which describe the innovative behaviour and the information activities of the enterprises. The questionnaire included questions about process and product innovations, the product age and the three fundamental components in the strategic management of enterprises: The attitude to risk, which is proved by the choice of the growth strategy and the regional extension of sales markets. The innovative competence, i.e. the existence of activities in the areas of research and development, construction and design, business planning and staff development. The willingness to learn and the acquisition of knowledge, i.e. the employees' capability and readiness to take up know-how and to realize innovations with this know-how. The paper summarises the most significant results of the study. The examined craft enterprises were divided into two different groups: the especially successful enterprises and the less successful enterprises. Compared with the less successful enterprises, the especially successful enterprises have a stronger attitude to risk, more innovative competences and a higher willingness to learn. The differences are also emphasized by the fact that successful enterprises formulate questions - not only at the beginning of the renewal process but during all their activities. By doing so they question about themselves and their traditional way of solving problems. They organize a permanent knowledge exchange.

Group Size and Social Ties in Microfinance Institutions

Microfinance programmes provide poor people with small loans given to jointly liable self-selected groups. Follow-up loans provide incentives to repay. In an experiment we investigate the influence of those features on strategic default. Each group member invests in an individual risky project, whose outcome is known only to the individual investor. Subjects decide, whether to contribute to group repayment or not. Only those with successful projects can contribute. The experiment ends if too few repay. We investigate group size and social ties effects. We observe high repayments rates, which are robust across treatment. Group lending outperforms individual lending. Self-selected groups show a high but less stable willingness to contribute.microcredits, group lending, public goods, laboratory experiments, development economics

Protective activity of aromatic amines and imines against oxidative nerve cell death

Oxidative stress is a widespread phenomenon in the pathology of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Neuronal cell death due to oxidative stress may causally contribute to the pathogeneses of these diseases. Therefore, neuroprotective antioxidants are considered to be a promising approach to slow down disease progression. We have investigated different aromatic amine and imine compounds for neuroprotective antioxidant functions in cell culture, and found that these compounds possess excellent cytoprotective potential in diverse paradigms of oxidative neuronal cell death, including clonal cell lines, primary cerebellar neurons, and organotypic hippocampal slice cultures. Aromatic amines and imines are effective against oxidative glutamate toxicity, glutathione depletion, and hydrogen peroxide toxicity. Their mode of action as direct antioxidants; was experimentally confirmed by electron spin resonance spectroscopy, cell-free brain lipid peroxidation assays, and intracellular peroxide measurements. With half-maximal effective concentrations of 20-75 nm in different neuroprotection experiments, the aromatic imines phenothiazine, phenoxazine, and iminostilbene proved to be about two orders of magnitude more effective than common phenolic antioxidants. This remarkable efficacy could be directly correlated to calculated properties of the compounds by means of a novel, quantitative structure-activity relationship model. We conclude that bridged bisarylimines with a single free NH-bond, such as iminostilbene, are superior neuroprotective antioxidants, and may be promising lead structures for rational drug development