Abstract
The article describes the methodology and psychometric evaluation of an assistive technology (AT) outcomes measurement tool, the Usability Scale for Assistive Technology-Wheeled Mobility module (USAT-WM), as a tool to capture user-centered usability of wheeled-mobility devices. The construction of the USAT-WM was driven by a qualitative inquiry focusing on the experiences of users of wheeled mobility devices. The interview content was coded and nearly 400 indicators pertaining to usability of wheeled-mobility devices were assimilated to construct a preliminary version of the USAT-WM. The content validity of the USAT-WM was evaluated by a panel of clinicians in the field of wheeled-mobility. The findings from the content validation process were utilized to revise the USAT-WM.
A field-test of the USAT-WM was conducted by administering it to 70 individuals who used power wheelchairs (PWCs) for mobility. A preliminary principal component analysis of the instrument sections was performed, and based on the item loading a subsequent factor analysis was conducted to establish a 50-item version of the USAT-WM with seven subscales: home usability; workplace/school usability; community usability; outdoor usability; ease of use; seating; and safety. Internal consistency Cronbach's alpha values for the seven subscales ranged from 0.77 to 0.91 and 0.90 for the total score of the USAT-WM. The test-retest and alternate-form reliability of the USAT-WM scores correlated at 0.85 (p < 0.01). The convergent validity correlations of the USAT-WM with the Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST2.0) and the Psychosocial Impact of Assistive Devices Scale (PIADS) were found to be 0.55 (p < 0.01) and 0.30 (p < 0.01) respectively.