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Forschungsseminar am Institut für Angewandte Statistik

18. Jänner

Ao.Univ.-Prof. Dipl.-Ing. Dr.techn. Herwig Friedl, Institute of Statistics, Graz University of Technology: Hands-on Applications of Mixture models (Joint work with Dankmar Böhning, Bettina Grün, Sanela Omerovic, Elisabeth Reitbauer & Peter Scheibelhofer)

Herwig Friedl

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Meeting-ID: 280 519 2121
Passwort: 584190


We will introduce this class of models by discussing three very different practical applications.

The first application is about estimating the hard-to-count size of a closed population. We consider uni-list approaches in which the count of identifications per unit is the basis of analysis. Unseen units have a zero count and do not occur in the sample leading to a zero-truncated setting. Due to various mechanisms one-inflation is often an occurring phenomena which can lead to seriously biased estimates of population size. The zero-truncated one-inflated and the one-inflated zero-truncated model is compared in terms of Horvitz-Thompson estimation of population size. The illustrative data is about the number of sightings of dice snakes in Graz.

In another study, we deal with black and white C-SAM images of wafer structures. The statistical analysis is based on the corresponding multimodal frequency histograms of the gray levels. The goal is to draw conclusions about both the quality of the wafers and the contrast of the images. A heterogeneous mixture of gamma densities together with a uniform distribution component is successfully used to enable such a dual defect analysis.

The last application deals with a mixture of generalized non-linear models for estimating the daily maximum gas consumption as a function of the outdoor temperature. For this purpose, we have implemented "flexmixNL" as an extension of the well-known R package "flexmix". This now allows the analysis by means of a homogeneous mixture of linear exponential families, where the means are modeled nonlinearly, here by a family of sigmoid functions. If we mix various components differently, this can be used to account for unobserved heterogeneity.


Datum & Uhrzeit


15:30 - 17:00 Uhr

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S2 Z74, Science Park 2