Abstract

This study was aimed to examine the reliability and validity of Weiss' Plan Formulation Method, one of the case formulation methods, which evaluates client's problem, therapist intervention and therapy outcome individually. Study 1 examined the interrater reliability on Plan Formulation's components. The average of interrater reliabilities on those were very high; .90 in goal, .93 in obstruction, .88 in test, .91 in insight. And the interrater agreement was moderate. Study 2 rated the plan compatibility of therapist intervention in the basis of plan formulation to examine the reliability of this method. The results were that the interrater reliabilities of two rating methods were very high; .80 in Individual Compatibility and .87 in Segment Compatibility, and interrater agreements were very high; .91 in Individual Compatibility and .82 in Segment Compatibility. Study 3 rated the client's dynamic change using Plan Attainment Scale to test the reliability of this scale, and to evaluate the relationships between this scale and six symptom measures. The interrater reliabilities of items about attaining goal, overcoming pathogenic belief, and overall attainment were high, but that of attaining insight item was low. In analysing the relationships between this scale and six symptom measures, it was found that this scale significantly correlated with composite symptom measure, counseling effect questionnaire and trait anxiety questionnaire. Study 4 tried to test the relationships between the plan compatibility and session outcome. The results were that plan compatibility was significantly correlated with session impact and therapeutic outcome. The implications and limitations of this study was discussed.