Effect of class imbalance on quality measures for contrast patterns

An experimental study of the effect of class imbalance on quality measures for contrast patterns is presented.Our study was performed both regarding and disregarding the class imbalance level.The best quality measures for ranking patterns in class imbalance problems is provided.A guide for determining, according to the class imbalance ratio, the quality measure to apply, is provided. Contrast pattern-based classifiers rely on the discriminative power of contrast patterns. For this reason, many quality measures have been proposed to evaluate the quality of a contrast pattern. These measures allow to distinguish among contrast patterns with low and high discriminative ability for classification. In the literature, many comparative studies among quality measures for contrast patterns have been proposed but all of them were performed without taking into account the class imbalance level. However, in many class imbalance problems, those patterns extracted from the minority class have low support, which could negatively affect their discriminative ability. Therefore, in this paper, we present an experimental study of the effect of class imbalance on quality measures for contrast patterns. This study determines which quality measures for contrast patterns are the best for class imbalance problems; both regarding and disregarding the class imbalance level. Also, for the best quality measures we performed a pairwise comparison to determine which other quality measures have statistically similar behavior to them. This will help to simplify future research since it can be used only one quality measure among those with similar performance.