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Activity Number:
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37
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Type:
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Contributed
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Date/Time:
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Sunday, August 2, 2009 : 2:00 PM to 3:50 PM
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Sponsor:
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Section on Bayesian Statistical Science
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| Abstract - #303991 |
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Title:
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Using Mixtures to Model Outliers in Inter-Laboratory Studies
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Author(s):
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Garritt L. Page*+ and Stephen B. Vardeman
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Companies:
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Iowa State University and Iowa State University
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Address:
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4003 Arkansas Dr., Ames, IA, 50014,
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Keywords:
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Inter-laboratory studies ; Outliers ; Finite Mixture
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Abstract:
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Inter-laboratory studies (especially Key-Comparisons) are conducted to ensure measurement capability for commerce and to evaluate both national and international equivalence of measurement. In these studies, a reference value of some measurand (the underlying quantity subject to measurement) is computed. How to determine the reference value is not completely obvious if there are labs that could be considered outliers. Since ignoring results from one or more participating laboratories is untenable in practical terms, developing methods that are robust to the possibility that a small fraction of the labs produce observations unlike those from the others is critical. We outline two Bayesian procedures of analyzing inter-laboratory data found in the literature and suggest three modifications that are more robust to outliers. A simulation study is conducted to compare the methods
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