Development of an instrument to measure usability of assistive technology devices
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Usability of assistive technology (AT) devices determines how effectively and efficiently AT users with disabilities can participate in various activities. This research program (dissertation) involved the conceptualization of the Usability Scale for Assistive Technology (USAT), and the development of the Wheeled Mobility module of the USAT, USAT-WM, as a tool to capture user-centered usability of wheeled-mobility devices. In human factors science, usability is considered to be an outcome of the interaction of the user with the product ( AT ) to accomplish a task (or activity ) under the influence of an environment . On this theme, a qualitative inquiry was conducted with users of AT devices focusing on their experiences with use of AT. The interview content was coded and nearly 400 indicators pertaining to wheeled-mobility AT 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. In order to promote the applicability of the USAT-WM, an intervention framework has been proposed. A descriptive analysis of the field-test data was conducted to identify and map usability issues associated with PWCs to this framework.