Convergent and discriminant validity of three measures of stage of change.

The University of Rhode Island Change Assessment (E. A. McConnaughy, J. O. Prochaska, & W. F. Velicer, 1983), the Stages of Change Readiness and Treatment Eagerness Scale (W. R. Miller & J. S. Tonigan, 1996), and the Readiness to Change Questionnaire (S. Rollnick, N. Heather, R. Gold, & W. Hall, 1992) are commonly used multidimensional measures of stage of change. The authors examined the convergent and discriminant validity of drug-use versions of these 3 measures through multitrait-multimethod analysis in a population of indigent, out-of-treatment drug users (N = 377). Agreement in stage-of-change assignment and the relationship between stage of change and drug-use behaviors were also examined. Confirmatory factor analysis suggests that the Stages of Change Readiness and Treatment Eagerness Scale may have questionable convergent validity with the University of Rhode Island Change Assessment and Readiness to Change Questionnaire. There was moderate agreement in stage assignment. Analysis of behavior did provide some support for the construct validity of the measures. The results suggest that these drug-use stage-of-change measures may not be equivalent.