Software evolution is an important activity in the life cycle of a modern software system. In the process of software evolution, the repair of historical defects and the increasing demands may introduce new defects. Therefore, evolution-oriented defect prediction has attracted much attention of researchers in recent years. At present, some researchers have proposed the process metrics to describe the characteristics of software evolution. However, compared with the traditional software defect

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... ediction methods, the research on evolution-oriented defect prediction is still inadequate. Based on the evolution data of object-oriented programs, this study presented two new process metrics from the defect rates of historical packages and the change degree of classes. To show the effectiveness of the proposed process metrics, the authors made comparisons with the code metrics and other process metrics. An empirical study was conducted on 33 versions of nine open-source projects. The results showed that adding the proposed process metrics could improve the performance of evolution-oriented defect prediction effectively.