The development and assessment of valid measures of service delivery to enhance inference in outcome-based research: measuring attendance at self-help group meetings.

The article focuses on the validity of measures of service delivery; any attempt to establish a linkage between service and outcomes follows the assumption that services have been given and received. Claims relating to the benefits of attending self-help groups on the mental health functioning of individuals with depression or manic depression were examined in the context of a well-controlled study and a validated measure of individual attendance. A test was conducted to probe the conjecture that the greater the degree of involvement in self-help groups, the greater the improvement in functioning. Additional questions related to individual patterns of attendance, generalization of the intervention's effects, and migration from "home" to other meeting sites.