The Usefulness, Satisfaction, and Ease of Use Questionnaire (USE, Lund, 2001) measures the subjective usability of a product or service. It is a 30-item survey that examines four dimensions of usability: usefulness, ease of use, ease of learning, and satisfaction. This metric can be applied to various scenarios of usability assessment because it is non-proprietary and technology-agnostic. Items in the USE also have good face validity with unambiguous and relevant descriptions. However, little published research has reported reliability or validity of the USE. The current study aims to address this issue by investigating psychometric properties of the USE. One hundred and fifty-one participants from Mechanical Turk (MTurk) evaluated Microsoft Word and Amazon.com on the USE and the System Usability Scale (SUS, Brooke, 1996). Ignoring the four dimensions in the USE, Cronbach’s alpha was .98, which indicates high reliability of overall USE score. The scale-reliability of dropping any item was .98 in both products. In terms of correlations between the USE dimensions and the SUS, validity was statistically and practically significant ( r between .60 and .82, p < .001). System sensitivity of the USE was also demonstrated via significant t-tests on the USE scores between Microsoft Word and Amazon.com . A principal axis factor analysis revealed a four-factor model that is different from the original model. Three factors resembled the original dimensions, and a fourth factor was related to multiple dimensions. Overall, the USE is a valid and reliable instrument that needs further refinement.

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As the trend of home-delivered healthcare grows, the number of healthcare devices being utilized in the home setting also increases greatly, but the usability of all these devices has not been systematically examined. While traditional in-lab usability testing is too time-consuming to make broad assessments of a large number of home healthcare devices, retrospective evaluation techniques using subjective usability surveys may be more promising because of their time and resource efficiency. However, the equivalence of data collected with these two techniques is not well understood for medical devices. This study collected usability data for multiple healthcare devices from 74 subjects in laboratory usability testing and 395 subjects using a retrospective assessment survey. Measures of overall subjective usability (measured using the System Usability Scale) and the ISO usability metrics of effectiveness, efficiency, and satisfaction were captured in both methods. Results show a consistency in satisfaction and overall subjective usability scores between the retrospective survey and laboratory testing, while measures of effectiveness and efficiency differed. These results suggest that retrospective surveys are capable of capturing the overall usability of a product by using the System Usability Scale metric. Such a finding should increase the confidence of researchers and practitioners who wish to use retrospective measures as a quick and economical technique in the large-scale assessment of medical devices. However, researchers should be cautious about measuring individual ISO usability metrics with retrospective surveys, as there are pronounced differences between lab-based usability testing and retrospective assessments.

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