Psychometric characteristics of the child occupational self-assessment (COSA), part two: refining the psychometric properties.

Self-assessment is an appropriate way to support client-centered practice and promote personal development in young occupational therapy clients. This study, the second study in a series of two, sought to refine the psychometric properties based on previous analysis of the Child Occupational Self-Assessment (COSA), a self-report tool based on the Model of Human Occupation. The COSA comprises 24 statements, which the child rates in terms of personal competence and importance. The Rasch Rating Scale Model was used to evaluate the measurement properties of the Competence and Values scales that result from these self-ratings. The original three-point rating scale was expanded to four response categories in this study, which resulted in improved reliability and sensitivity. In this second study, the items once again coalesced to form measures of competence and values, and the order of items from less to more competence and value was similar to that in the first study, supporting the internal validity of the COSA scales. The results provide evidence that the COSA can be used as meaningful and reliable client-directed assessment tool as well as an outcome measure.