## ZüKoSt: Seminar on applied Statistics

Time/Place: every Thursday at 4.15 pm at the Main Building of ETH, HG G 19.1

### Spring Semester 2010

Organiser(s)

Date Speaker Title Time Location
11-mar-2010 (thu)
Willi Maurer
A Graphical Approach to Sequentially Rejective Multiple Test Procedures and its Application in Clinical Trials 16:15-17:30 HG G 19.1
 Abstract: In confirmatory clinical trials the Type I error rate must be controlled for claims forming the basis for approval and labelling of a new drug. Strong control of the familywise error rate is usually needed for families of hypotheses related to the claims. Such families of hypotheses arise naturally from comparing several treatments with a control, combined non-inferiority and superiority testing for primary and secondary variables, the presence of multiple primary or secondary endpoints and combinations thereof. A variety of sequentially rejective, weighted Bonferroni type tests have been proposed for this purpose, such as parallel and serial gatekeeping procedures. They allow -in principle- mapping the partially hierarchical structure with respect to importance of hypotheses onto multiple test procedures. Since these procedures are based on the closed testing principle they require the explicit specification of a large number of intersection hypotheses tests. For a procedure defined this way it is difficult to recognize the basic principle behind the choice and vice versa. In this talk a graphical approach* for constructing and performing the test procedure is presented. The relative importance of the hypotheses and their partially hierarchical structure is mapped onto weighted directed graphs whose vertices are representing the hypotheses. An update algorithm for the graphs enables sequentially rejective testing. Some properties of procedures generated this way are discussed and are illustrated with the visualization of common gatekeeping strategies and of procedures for more complex testing situations that have arisen in clinical practice. * Bretz, F., Maurer, W., Brannath, W., and Posch, M. (2009), A graphical approach to sequentially rejective multiple test procedures,'' Statistics in Medicine, 28, 586-604. Speakers: Willi Maurer (Novartis Pharma AG)
15-apr-2010 (thu)
Dalalyan Arnak
Robust Estimation for an Inverse Problem Arising in Multiview Geometry 16:15-17:30 HG G 19.1
 Abstract: (joint work with R. Keriven) We propose a new approach to the problem of robust estimation for an inverse problem arising in multiview geometry. Inspired by recent advances in the statistical theory of recovering sparse vectors,we define our estimator as a Bayesian maximum a posteriori with multivariate Laplace prior on the vector describing the outliers. This leads to an estimator in which the fidelity to the data is measured by the L_\infty - norm while the regularization is done by the L1-norm. The proposed procedure is fairly fast since the outlier removal is done by solving one linear program (LP). An important difference compared to existing algorithms is that for our estimator it is not necessary to specify neither the number nor the proportion of the outliers; only an upper bound on the maximal measurement error for the inliers should be specified. We present theoretical results assessing the accuracy of our procedure, as well as numerical examples illustrating its efficiency on synthetic and real data. Speakers: Dalalyan Arnak (Ecole des Ponts Paris Tech)
22-apr-2010 (thu)
Berend Snijder
Single cell modeling in image based RNAi screens 16:15-17:30 HG G 19.1
 Abstract: Systematically interfering with the components that make up a larger system is a good way of getting first insights into how the system works. In molecular cell biology, RNA interference (RNAi) has become the method of choice to silence individual genes, the building blocks of life. We use RNAi to silence thousands of human genes, one at the time, in order to find out which of these genes are required for virus infection. Automated microscopy combined with high content image analysis is used to get quantitative readouts of the many millions of cells that make up such large scale screens. Using these methods we discovered that virus infection in human cells is much more complex than previously assumed, with different viruses preferentially infecting different sub-populations of cells. We therefore apply several statistical methods to model single-cell behavior in our RNAi screens. Although these statistics add a layer of complexity to the process of RNAi screening, we find that the quality and types of information we can extract from RNAi screens is greatly increased. The improved understanding of cellular behavior and virus infection opens up new avenues in the search for antiviral drug targets, and the methods described here generalize to many different types of cellular perturbation screens. Speakers: Berend Snijder (ETH Zürich)
29-apr-2010 (thu)
Statistics with a human face 16:15-17:30 HG G 19.1
 Abstract: Three-dimensional surface imaging, through laser-scanning or stereo-photogrammetry, provides high-resolution data defining the shape of objects. In an anatomical setting this can provide invaluable quantitative information, for example on the success of surgery. Two particular applications are in the success of breast reconstruction and in facial surgery following conditions such as cleft lip and palate. An initial challenge is to extract suitable information from these images, to characterise the surface shape in an informative manner. Landmarks are traditionally used to good effect but these clearly do not adequately represent the very much richer information present in each digitised images. Curves with clear anatomical meaning provide a good compromise between informative representations of shape and simplicity of structure. Some of the issues involved in analysing data of this type will be discussed and illustrated. Modelling issues include the measurement of asymmetry and longitudinal patterns of growth. Speakers: Bowman Adrian (University of Glasgow, UK)
27-may-2010 (thu)
Roger Kaufmann
Fussball-Mathematik: Vorhersagen zur Weltmeisterschaft (findet in HG G 5 statt) 16:15-17:30 HG G 5
 Abstract: Der Ausgang eines Fussballspiels ist im Voraus unklar, was den grossen Reiz dieses Sports ausmacht. Aber ist Fussball unvorhersehbar? Wir diskutieren diese Frage anhand der FIFA WM 2010 in Südafrika. In einem ersten Teil wird der Zusammenhang zwischen Fussball und Mathematik aufgezeigt. Ein mathematischer Ansatz zur Berechnung möglicher Ausgänge von Fussballspielen wird präsentiert. Anschliessend werfen wir einen Blick auf die Partie Schweiz - Spanien, die am 16. Juni in Südafrika über die Bühne gehen wird. Im letzten Teil der Präsentation sprechen wir über Backtesting und zeigen auf, wie Fussballmanager von solchen Berechnungen profitieren können. Der Grossteil des Vortrags wird für Hörer/innen ohne statistische Fachkenntnisse verständlich sein. The talk will be in German, with English slides. Speakers: Roger Kaufmann

Further information: sekretariat@stat.math.ethz.ch
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