Development and initial validation of the Assessment of Motivational Interviewing Groups-Observer Scales (AMIGOS)

This article documents the development and initial validation of a global observer instrument, the Assessment of Motivational Interviewing Groups – Observer Scales (AMIGOS). The AMIGOS includes three scales composed of 18 items documenting group processes, client-centered style, and motivational interviewing (MI) change focus. Three experienced coders independently rated 18 sessions of various group approaches. The AMIGOS showed high inter-rater intraclass correlation coefficient (ICC) and Cronbach’s alpha, strong convergent and discriminant validity with the MI Treatment Integrity scales (MITI), the Therapist Empathy Scale (TES), and the Group Climate Questionnaire (GCQ). The AMIGOS shows promise as a reliable and valid measure of MI group leadership and group processes, and could be useful measuring other group therapies as well.