Psychometrics of the personal questionnaire: a client-generated outcome measure

Abstract

We present a range of evidence for the reliability and validity of data generated by the Personal Questionnaire (PQ), a client-generated individualized outcome measure, using 5 data sets from 3 countries. Overall pretherapy mean internal consistency (alpha) across clients was .80, and within-client alphas averaged .77; clients typically had 1 or 2 items that did not vary with the other items. Analyses of temporal structure indicated high levels of between-clients variance (58%), moderate pretherapy test-retest correlation (r = .57), and high session-to-session Lag-1 autocorrelation (. 82). Scores on the PQ provided clear evidence of convergence with a range of outcome measures (within-client r = .41). Mean pre-post effects were large (d = 1.25). The results support a revised caseness cutoff of 3.25 and a reliable change index interval of 1.67. We conclude that PQ data meet criteria for evidence-based, norm-referenced measurement of client psychological distress for supporting psychotherapy practice and research.