Standard Article


Statistical Theory and Methods

  1. Stefan Van Aelst

Published Online: 15 JAN 2013

DOI: 10.1002/9780470057339.vao019.pub2

Encyclopedia of Environmetrics

Encyclopedia of Environmetrics

How to Cite

Van Aelst, S. 2013. Outliers. Encyclopedia of Environmetrics. 4.

Author Information

  1. Ghent University, Gent, Belgium

Publication History

  1. Published Online: 15 JAN 2013


Datasets frequently contain outliers which are observations that strongly deviate from the pattern in the majority of the data. Detecting outliers and measuring their influence on an estimation procedure is not trivial. In one or two dimensions graphical inspection of the data may be helpful, but in higher dimensions more reliable methods are needed. We discuss robust estimation to obtain estimates that can resist the influence of outliers and related outlier diagnostics to identify the outliers in a dataset.


  • contamination;
  • model deviation;
  • diagnostics;
  • influential points;
  • outlier detection;
  • robustness