A pattern is considered useful if it can be used to help a person to achieve his goal. Mining data streams for useful patterns is important in many applications. However, data stream can change their behavior over time and, when significant change occurs, much harm is done to the mining result if it is not properly handled. In the past, there have been many studies mainly on adapting to changes in data streams. We contend that adapting to changes is simply not enough. The ability to detect and characterize change is also essential in many applications, for example intrusion detection, network traffic analysis, data streams from intensive care units etc. Detecting changes is nontrivial. In this paper, an online algorithm for change detection in utility mining is proposed. In order to provide a mechanism for making quantitative description of the detected change, we adopt the statistical test. We believe there is the opportunity for an immensely rewarding synergy between data mining an...