Rasch Analysis of the Profiles of Occupational Engagement in people with Severe mental illness (POES) instrument

PURPOSE The Profiles of Occupational Engagement in people with Severe mental illness (POES) instrument was developed to study time use profiles of occupations and measure the extent they are characterized by engagement. However, the dimensional factors are not known. The aim of the present study was to establish the internal construct validity of the POES using the Rasch measurement model. METHODS A sample of 192 outpatients in Sweden was administered the POES and data were subjected to Rasch analysis. RESULTS The POES showed good fit to the Rasch model after accommodation for local dependency. The nine items had high reliability as measured by person separation index, and no threshold disordering was present. Differential item functioning analysis showed no significant differences across groups of age, sex, diagnosis, or country of origin. CONCLUSION The POES is a unidimensional scale that represents a continuum of occupational engagement. The transformed POES sum score can be used on an interval scale to measure status and changes in occupational engagement in mental health practice and research.