It is possible that exogenous variables developed during the study, including treatment refiisal, discharge from hospital, employment, or dismissal. However, increasing group size and sequential tests could reduce such exogenous variables. Kim (2004) conducted a lZ-session anger management program three times a week for victims of intimacy violence; No significant differences were found in the posttest Korean Anger Expression Inventory scores between the experimental and'bontrol groups in the first month (P = .104). The significance of the program was revealed by the follow-up test conducted 1 month after the posttest. In the follow-up test, the effect size was extremely large (P = .001). This suggests that the effects of anger management programs appeared slowly and were maintained for a long time without additional intervention, which indicates that the program was efficacious. Therefore, to measure program efficacy more effectively, sequential follow-up tests and longitudinal data should be planned. In addition, it 'is encouraged to include qualitative methodology for describing participants’ experiences and internal changes during the program.