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Zijlstra, Wobbe

Detection of out liers in test, questionnaire and survey data

Wobbe Zijlstra (PhD student)
Department of Methodology
Faculty of Social Sciences, Tilburg University
P.O. Box 90153
5000 LE Tilburg

Phone: +31 13 466 3270 / 2544 (secretary)
E-mail: Wobbe Zijlstra

Supervisors: Prof. dr K. Sijtsma, dr A. Van der Ark
Project: NWO project at Tilburg University
Project running from: 1 September 2005 – 1 September 2009

Summary

Outliers, often defined as observat ions, which are inconsistent with the remaining data, are influent ial to the degree in which they affect stat ist ical results. Out lier research is often done with cont inuous variables, such as income and age. This project defines out liers for highly discrete data in test , quest ionnaire and survey data, and proposes several methods for detect ing out liers. I t is also invest igated when an out lier is influent ial, and how to deal with influent ial cases. Simulated and numerous real data sets are used. The project will result in user – friendly software for handling data quality problems, including out lier analysis.

Date of defence:
Title of thesis: