Benefits of empirically supported interventions hinge on clinician skill, particularly for motivational interviewing (MI). Existing MI skill assessments are limited with respect to validity (e.g., self-report) and practicality (e.g., coding session tapes). To address these limitations, we developed and evaluated two versions of a web-based assessment of MI skills, the Computer Assessment of Simulated Patient Interviews (CASPI). Ninety-six counselors from the community and 24 members of the Motivational Interviewing Network of Trainers (MINT) completed the CASPI (N = 120), in which they verbally responded via microphones to video clips comprising three 9-item vignettes. Three coders used an emergent coding scheme, which was compared with alternative MI skills measures.
CASPI demonstrated excellent internal consistency when averaging across two or three vignettes (α's = .86–.89). Intraclass correlations were above .40 for most items. Confirmatory factor analyses supported a correlated three-factor model: MI-consistent, resistance-engendering, and global change talk orientation rating. Means and factor loadings were invariant across forms (i.e., the two alternative versions of CASPI), and factor loadings were invariant across subgroup (i.e., community counselor or MINT member). Test–retest reliability was good for MI-consistent and resistance-engendering scores (r = .74 and .80, respectively) but low for change talk orientation (r = .29) unless coder was taken into account (r = .69). CASPI showed excellent construct and criterion-related validity.
CASPI represents a promising method of assessing MI skills. Future studies are needed to establish its performance in real-world contexts.
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