Data Mining: Concepts and Techniques, 3rd Edition

12.9 Summary

■ Assume that a given statistical process is used to generate a set of data objects. An outlier is a data object that deviates significantly from the rest of the objects, as if it were generated by a different mechanism.

■ Types of outliers include global outliers, contextual outliers, and collective outliers. An object may be more than one type of outlier.

■ Global outliers are the simplest form of outlier and the easiest to detect. A contextual outlier deviates significantly with respect to a specific context of the object (e.g., a Toronto temperature value of 28° C is an outlier if it occurs in the context of winter). A subset of data objects forms a collective outlier if the objects as a whole deviate significantly from the entire ...