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Search Results: 1 - 10 of 6112 matches for " MARKUS SOMMER "
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The effect of success probability on test economy and self-confidence in computerized adaptive tests
JOACHIM H?USLER,MARKUS SOMMER
Psychology Science Quarterly , 2008,
Abstract: Recent research on the psychological effects of different design decisions in computerized adaptive tests indicates that the maximum-information item selection rule fails to optimize respondents’ test-taking motivation. While several recent studies have investigated psychological reactions to computerized adaptive tests using a consistently higher base success rate, little research has so far been conducted on the psychometric (primarily test reliability and bias) and psychological effects (e.g. test-taking motivation, self-confidence) of using mixtures of highly informative (p = .50) and easier items (p = .80) in the item selection process. The present paper thus compares these modifications to item selection with a classical maximum-information algorithm. In a simulation study the effect of the different item selection algorithms on measurement precision and bias in the person parameter estimates is evaluated. To do so, the item pool of the Lexical Knowledge Test, measuring crystallized intelligence and self-confidence, is used. The study indicated that modifications using base success probabilities over p = .70 lead to reduced measurement accuracy and - more seriously - a bias in the person parameter estimates for higher ability respondents. However, this was not the case for the motivator item algorithm, occasionally administering easier items as well. The second study (n = 191) thus compared the unmodified maximum-information algorithm with two motivator item algorithms, which differed with regard to the percentage of motivator items presented. The results indicate that respondents yield higher self-confidence estimates under the motivator item conditions. Furthermore, the three conditions did not differ from each other with regard to the total test duration. It can be concluded that a small number of easier motivator items is sufficient to preserve test-taking motivation throughout the test without a loss of test economy.
Optimizing technical precision of measurement in computerized psychological assessment on Windows platforms
JOACHIM H?USLER,MARKUS SOMMER,STEFAN CHROUST
Psychology Science , 2007,
Abstract: Reaction times and response latencies are required to measure a variety of ability and personality traits. If reaction times are used to measure rather elementary cognitive tasks, the inter-individual variance in the measured reaction times are usually small in the sense that the central 50 percent of a norm population range within less than 100ms. Technical measurement errors therefore have the potential to seriously affect the validity of diagnostic judgments based on such measures. Thus the target of this paper is to investigate the magnitude of possible errors of measurement due to technical reasons and to suggest ways to prevent or at least consider those in the diagnostic process.In Study I a highly precise 'artificial respondent' was applied to simulate reactions corresponding to a given percentile rank on 3 different tests (DG-Lokation CORPORAL, Alertness TAP-M, RT/S9 Vienna Test System) on 11 different computer systems. The result output of the tests was compared to the reaction times, actually provided by the artificial respondent. Results show, that there are detectable errors of measurement - depending on the hardware and software specifications of the computer system used. In the test DG-Lokation these bias caused an offset in the tests main variable of up to 20 percentile ranks.In Study II a self-calibration unit which is part of the Vienna Test System (Version 6.40) was investigated, using the same experimental setup. After calibration, the bias detected can be reduced to the magnitude of about 1 percentile rank on all computer systems tested.It thus can be concluded, that time critical computer based tests typically bear the risk of technical errors of measurement. Depending on how the test is programmed, the errors arising on some computer configurations can cause even severe changes in diagnostic judgment formation. In contrast, self-calibration proved to be an effective tool to permitting the user not only to control but also to ensure the precision of measurement, independent of the properties of the computer system he is administering his test on.
FTY720 Reduces Post-Ischemic Brain Lymphocyte Influx but Does Not Improve Outcome in Permanent Murine Cerebral Ischemia
Arthur Liesz, Li Sun, Wei Zhou, S?nke Schwarting, Eva Mracsko, Markus Zorn, Henrike Bauer, Clemens Sommer, Roland Veltkamp
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0021312
Abstract: Background The contribution of neuroinflammation and specifically brain lymphocyte invasion is increasingly recognised as a substantial pathophysiological mechanism after stroke. FTY720 is a potent treatment for primary neuroinflammatory diseases by inhibiting lymphocyte circulation and brain immigration. Previous studies using transient focal ischemia models showed a protective effect of FTY720 but did only partially characterize the involved pathways. We tested the neuroprotective properties of FTY720 in permanent and transient cortical ischemia and analyzed the underlying neuroimmunological mechanisms. Methodology/Principal Findings FTY720 treatment resulted in substantial reduction of circulating lymphocytes while blood monocyte counts were significantly increased. The number of histologically and flow cytometrically analyzed brain invading T- and B lymphocytes was significantly reduced in FTY720 treated mice. However, despite testing a variety of treatment protocols, infarct volume and behavioural dysfunction were not reduced 7d after permanent occlusion of the distal middle cerebral artery (MCAO). Additionally, we did not measure a significant reduction in infarct volume at 24h after 60 min filament-induced MCAO, and did not see differences in brain edema between PBS and FTY720 treatment. Analysis of brain cytokine expression revealed complex effects of FTY720 on postischemic neuroinflammation comprising a substantial reduction of delayed proinflammatory cytokine expression at 3d but an early increase of IL-1β and IFN-γ at 24 h after MCAO. Also, serum cytokine levels of IL-6 and TNF-α were increased in FTY720 treated animals compared to controls. Conclusions/Significance In the present study we were able to detect a reduction of lymphocyte brain invasion by FTY720 but could not achieve a significant reduction of infarct volumes and behavioural dysfunction. This lack of neuroprotection despite effective lymphopenia might be attributed to a divergent impact of FTY720 on cytokine expression and possible activation of innate immune cells after brain ischemia.
The interrelationship between metabolic parameters in blood serum of cattle and fertility
H Sommer
Genetics Selection Evolution , 1976, DOI: 10.1186/1297-9686-8-2-295c
Abstract:
The importance of immune gene variability (MHC) in evolutionary ecology and conservation
Simone Sommer
Frontiers in Zoology , 2005, DOI: 10.1186/1742-9994-2-16
Abstract: Many natural populations are threatened not only by a dramatic reduction in total area of available habitat but also by increasing habitat fragmentation and degradation leading to declining population sizes and barriers to gene flow if exchange of individuals between subpopulations is restricted [1-3]. Small populations often suffer from reduction of genetic diversity due to genetic drift and inbreeding effects [4-6]. Negative effects such as increased rates of allelic loss, fixation of deleterious alleles and decreased average individual heterozygosity relative to the overall population were observed by both, theoretical and empirical studies [7,8]. The loss of genetic variation can lead to short-term reduction of fitness components such as survival, reproductive output, growth rates and to impaired ability to adapt to long-term changes in the environment [7,9-13]. An increasing number of studies indicates that host genetic diversity plays an important role in buffering populations against pathogens and widespread epidemics [6,14-20]. Study of the genetic effects of population fragmentation is therefore of central importance for conservation biology [21].Genetic studies of wild animals often employ neutral markers such as mitochondrial d-loop DNA (mtDNA), microsatellites or single nucleotide polymorphism (SNPs) to estimate the amount of variation present in individuals and populations [22-24]. While these markers are very informative for phylogenetic reconstructions and population history (bottleneck effects), for molecular clocks, to examine dispersal patterns of individuals (gene flow) and to classify individuals by relatedness and paternity analyses [25-28], the variation at neutral loci cannot provide direct information on selective processes involving the interaction of individuals with their environment or on the capacity for future adaptive changes [29,30]. However, these are issues of particular relevance in evolutionary ecology and conservation [31,32]. In
Upper-School Teaching at Steiner Waldorf Schools: Cognitive Challenges for the Embodied Self
Wilfried Sommer
RoSE : Research on Steiner Education , 2010,
Abstract: The processes at work in Steiner Waldorf (hereafter ‘Waldorf’) upper school teaching show specific characteristics. They address, for example, heterogeneous learning groups, structuring the learning process in a manner that engenders in the student communication with the world and with themselves. The didactic preparation of teaching material should not merely facilitate this but also consider the embodied self with its diverse life modes. This process shall be considered in the language of phenomenological anthropology. The dialectics of the centric and eccentric positions will be the subject of discussion as will be the significance of engaged and detached perspectives.Part I of this article, in this issue, discusses not only the teaching processes but also their philosophical setting. Two concrete examples from the classroom illustrate how this then translates into the appropriate path in practical teaching. In the next issue, Part II of the article will examine classroom methodology. This will discuss how classroom practice can help students, as embodied persons, to relate to their need for intellectual positioning and thus develop a way of thinking that does not alienate them from themselves as persons but puts their embodied, personal existence into context.
Oberstufenunterricht an der Waldorfschule: Kognitive Herausforderungen für das verk rperte Selbst
Wilfried Sommer
RoSE : Research on Steiner Education , 2010,
Abstract: Zusammenfassung. Die Unterrichtsprozesse in der Oberstufe Freier Waldorfschulen weisen spezifische Merkmale auf: Sie wenden sich z.B. an heterogene Lerngruppen und legen dort das Lernen so an, dass es sich zu einem Verst ndigungsprozess mit der Welt und mit sich selbst entwickeln kann. Die didaktische Aufbereitung der Unterrichtsinhalte muss das nicht nur zulassen, sondern auch das verk rperte Selbst mit seinen unterschiedlichen Lebensmodi berücksichtigen. Dieser Rahmen soll in der Sprache der ph nomenologischen Anthropologie charakterisiert werden. Die Dialektik von zentrischer und exzentrischer Position wird ebenso wie die Rolle von eingebundener und abgel ster Perspektive thematisiert.In einem ersten Teil kommen in dieser Ausgabe nicht nur die Unterrichtsprozesse zur Sprache, sondern auch deren philosophisches Umfeld. An zwei konkreten Unterrichtsbeispielen wird dann der entsprechende Weg in die p dagogische Praxis verdeutlicht. In der n chsten Ausgabe soll in einem zweiten Teil die Unterrichtsmethodik untersucht werden. Hier wird es um die Frage gehen, wie Schülerinnen und Schüler durch die Unterrichtspraxis ihr Bedürfnis nach intellektueller Verortung auch auf sich als verk rperte Personen beziehen und damit ein Denken entwickeln k nnen, das sie nicht von sich als Personen entfremdet, sondern vielmehr ihr verleiblichtes personales Dasein in Zusammenh nge stellt.
Persistent Identifiers: the ‘URN Granular’ Project of the German National Library and the University and State Library Halle
Dorothea Sommer
Liber Quarterly : The Journal of European Research Libraries , 2010,
Abstract: This paper describes a project carried out by the German National Library, the University and State Library Sachsen-Anhalt in Halle and Semantics GmbH Aachen to establish routines of persistent identification for individual pages of web publications in order to enable and facilitate reliable and long-term valid citation practices for the academic community. The project originated in a pilot project to digitise approximately 10,000 German imprints from the seventeenth century comprising altogether about 600,000 pages, which had to be completed within two years. The material of the ‘Ponickau Collection’ had been catalogued in the German national bibliography of seventeenth-century imprints (VD 17), which was enriched and turned into a virtual library by adding the digitised texts. This article investigates the means of presentation and indexing of digitised imprints in order to ensure their usability. It also sketches the workflow among the various partners involved in the process. The article highlights the application of Visual Library, which contains various tools for automated creation of metadata, the implementation of persistent identifiers (URN) and the automated enrichment of catalogue entries by the regional cataloguing cooperative Gemeinsamer Bibliotheksverbund (GBV). Special emphasis is given to questions of quality management; the quality is guaranteed by a combination of automated tools and intellectual control at various stages of the digitisation process.
Boenninghausen and statistics. Boenninghausen y la estad -stica. Boenninghausen e a estat -stica.
Miriam Sommer
International Journal of High Dilution Research , 2005,
Abstract: This paper forms an introductory note to a number of papers discussing selected topics in homeopathy research. The objective is to provide a basic background to understand the way Boenninghausen build his “Therapeutisches Taschenbuch” and interpret the way he added the information taken from the Materia Medica Pura and clinical confirmation so we can apply it and add the modern material to the original repertory. To meet these challenges, knowledge is required: first, we need to know the way he took the symptoms from the Materia Medica Pura; second, we need to know how he matched these symptoms with the clinical confirmations. And finally, we need to execute a modern statistics analysis of the original material so will be able to formulate a prediction rule to apply to the modern material with the aim to add it to his original work.
Absent Causes, or el secreto a voces
Doris Sommer
Hispanic Issues On Line , 2009,
Abstract:
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