The development of the Therapy Presupposition Inventory (TPI)

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The authors describe 3 interrelated investigations in the development of the Therapy Presupposition Inventory (TPI). The TPI was designed to measure therapist presuppositions to assess therapist compatibility with treatment methods. Compatibility is associated with greater treatment fidelity and better treatment outcome. Forty-one items were developed through an inductive process of peer and literature review. Principal component analysis suggested a five-factor structure. Confirmatory factor analysis further validated the five-factor structure. For the final 20-item scale, results indicated adequate levels of reliability and internal consistency with alpha levels ranging from .68 to .81 among the five subscales and .78 for the overall scale. Correlations among the five TPI subscales ranged from .27 to .62, demonstrating each subscale has distinct conceptual properties. Test-retest correlations ranged from .59 to .87 {Md = .76). Acceptable convergent validity was established by examining predicted relationships between the TPI subscales and scales purportedly measuring similar constructs. Construct validity appears adequate for the TPI Collectivist Subscale; however, further construct validation studies are required for the remaining scales. Lastly, a treatment fidelity study demonstrates the TPI Collectivist Subscale correlated with therapist fidelity to Structural Family Therapy when students enter the training and 9 months later upon completion. Accordingly, findings provide support for the validity of the TPI Collectivist Scale; however, the other scales remain experimental. © NAJP.

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North American Journal of Psychology

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