Detecting outliers and/or leverage points: a robust two-stage procedure with bootstrap cut-off points

<p>This paper presents a robust two-stage procedure for identification of outlying observations in regression analysis. The exploratory stage identifies leverage points and vertical outliers through a robust distance estimator based on Minimum Covariance Determinant (MCD). After deletion of th...

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Bibliographic Details
Main Authors: Ettore Marubini, Annalisa Orenti
Format: Article
Language:English
Published: Milano University Press 2014-01-01
Series:Epidemiology, Biostatistics and Public Health
Online Access:http://ebph.it/article/view/9094
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Summary:<p>This paper presents a robust two-stage procedure for identification of outlying observations in regression analysis. The exploratory stage identifies leverage points and vertical outliers through a robust distance estimator based on Minimum Covariance Determinant (MCD). After deletion of these points, the confirmatory stage carries out an Ordinary Least Squares (OLS) analysis on the remaining subset of data and investigates the effect of adding back in the previously deleted observations. Cut-off points pertinent to different diagnostics are generated by bootstrapping and the cases are definitely labelled as good-leverage, bad-leverage, vertical outliers and typical cases. The procedure is applied to four examples.</p>
ISSN:2282-0930