Establishing clinically significant change: increment of precision and the distinction between individual and group...

Some essential adaptations to the method for determining clinically significant change originally introduced by Jacobson, Follette and Revenstorf [Jacobson, N. S., Follette, W. C. & Revenstorf, D. (1984a). Psychotherapy outcome research: methods for reporting variability and evaluating clinical significance. Behavior Therapy, 15, 336-352.] are presented. One adaptation deals with the failure in the original method to distinguish between analysis at the individual versus analysis at the group level. A second adaptation entails the provision of a closer approximation of the underlying true scores. This refinement represents an enhancement in precision. Specific aspects of this refinement may be understood in terms of a correction for error-based regression to the mean. Taking into account these adaptations, new procedures are described for determining (clinically significant) change. Some guidelines for the publication of outcome findings are also presented.