Class imbalance treatment methods and cost-sensitive classification algorithms are typically treated as two independent research areas. However, many of these techniques have properties in common. After providing a background to the two fields of research, this article identifies the fundamental mechanism which is common to both. Using this mechanism, a taxonomy is created which encompasses approaches to both class imbalance treatment and cost-sensitive classification. Through this survey, we aim to bridge the gap between the two fields such that lessons from one field may be applied to the other. Many data mining tasks are naturally both class imbalanced and cost-sensitive. This survey is useful for researchers and practitioners approaching these tasks as it provides a detailed overview of approaches in both fields. Many of the surveyed techniques are classifier independent. However, we chose to focus on techniques which were either decision tree-based or compatible with decision trees. This choice was based on the popularity and novelty of their application to both fields.