This article explores the effectiveness of test case prioritization techniques in improving the rate of fault detection during regression testing. The authors conducted a series of empirical studies to address three key questions: whether version-specific prioritization can improve fault detection, how fine-granularity and coarse-granularity techniques compare, and whether incorporating fault proneness measures can enhance prioritization effectiveness. The studies used both controlled experiments and case studies on various programs, including small and large programs with multiple versions. The results show that all prioritization techniques generally improve fault detection rates, with fine-granularity techniques outperforming coarse-granularity techniques by a small margin. Incorporating fault proneness measures had a relatively minor impact on fault detection rates. The effectiveness of different techniques varied across target programs, and the practical significance of these differences depends on the cost factors associated with testing processes. The article concludes by discussing the implications of these findings and suggesting areas for further research.This article explores the effectiveness of test case prioritization techniques in improving the rate of fault detection during regression testing. The authors conducted a series of empirical studies to address three key questions: whether version-specific prioritization can improve fault detection, how fine-granularity and coarse-granularity techniques compare, and whether incorporating fault proneness measures can enhance prioritization effectiveness. The studies used both controlled experiments and case studies on various programs, including small and large programs with multiple versions. The results show that all prioritization techniques generally improve fault detection rates, with fine-granularity techniques outperforming coarse-granularity techniques by a small margin. Incorporating fault proneness measures had a relatively minor impact on fault detection rates. The effectiveness of different techniques varied across target programs, and the practical significance of these differences depends on the cost factors associated with testing processes. The article concludes by discussing the implications of these findings and suggesting areas for further research.