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

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.