Construct validity of a measure of relative mastery based on the theory of occupational adaptation

The Relative Mastery Measurement Scale (RMMS), based on the theory of Occupational Adaptation, was developed to measure clients' perception of their occupational functioning. The specific construct measured by the RMMS is relative mastery which is a proposed indicator of occupational adaptation. Based on Schkade and Schultz's (1998) definition of relative mastery, the instrument includes items related to one's sense of effectiveness, efficiency, and satisfaction to self and society. This line of research examined the content and construct validity of this measure of occupational adaptation. The first study statistically evaluated the content validity of the RMMS based on the ratings of 6 experts in Occupational Adaptation. In the second and third studies, the construct validity of the RMMS was examined using a combination of Rasch analysis and traditional measurement statistics. Participants were 275 rehabilitation clients. Findings of the first study resulted in the experts' excellent agreement that the 12 RMMS items defined the construct of relative mastery. Results of the second and third studies provided preliminary evidence of the validity of the RMMS as a measure of relative mastery for adult clients undergoing rehabilitation. It appears that with continued development, the RMMS has potential to quantitatively measure clients' phenomenological experience of relative mastery as defined by the theory of Occupational Adaptation. Contributions of this line of research included: (a) preliminary support for the validity of the RMMS as a measure of relative mastery, (b) support for the construct of relative mastery as postulated by the theory of Occupational Adaptation, (c) advancement of the profession in available assessment procedures for involving clients in assessment and treatment planning, and (d) the application of measurement rigor in developing a measure of a phenomenological construct.