Usability Evaluation of Medical Technology: Investigating the Effect of User Background and Users' Expertise
Doktorsavhandling, 2009

Medical devices play a major role in diagnosis and therapeutics in the healthcare systems. The basic features of medical devices concern safety and efficient clinical performance. Nowadays, usability evaluation is an important part of the design process of medical devices. The aims of this thesis work were to investigate the effect of user profiles on usability evaluation results and to provide practical advice on choice of users as test subjects when conducting usability evaluations of medical devices. Five studies, with analytical and empirical evaluation approaches with different foci, were included in the work. In the studies, consideration was given to user background and users’ expertise as well as to user interfaces of different levels of complexity. The user background aspect was taken as the focus for the analytical evaluation approach, while users’ expertise was taken as the focus for the empirical evaluation approach. Cognitive Walkthrough was employed as an example of an analytical evaluation method to investigate user background, while usability tests were used as an example of empirical evaluation method to investigate users’ expertise. The results showed that medical device user background settings can influence the outcome of an analytical evaluation results, i.e. when more ergonomic factors were included in the user background settings, a wider range of usability problems were detected. User expertise is an important factor for the results of empirical usability tests. Users’ familiarity with tasks can be used as an important criterion for classification of user expertise. The quantitative analysis of the empirical evaluations implies that the effect of users’ expertise may be invisible when interacting with a simple user interface, but visible when interacting with a more complex user interface. Expert users outperformed novice users when interacting with a complex interface but not when interacting with a simple interface. The qualitative analysis of verbal explanations and statements, causes of errors and redesign proposals stressed the differences between novice and expert users in terms of decision-making, presentation and judgment, which implied that expert users’ use experience and novice users’ interaction experience differ in contributing to product design and development. Insufficient domain and interaction knowledge were consistently identified as typical causes of errors for novice users. The differences of information organization between previously experienced user interfaces and the interfaces interacted in the usability tests affected expert users’ task completion. Expert users made task-related errors due to terminology issues and interaction-related errors due to their ‘old’ mental model of how to interact with the user interface. Based on the results, different strategies are suggested to be used when choosing test subjects for usability evaluations in different interaction situations. A guideline and some practical advices were proposed as well to medical industrial companies about how to conduct usability evaluations on medical devices.

usability test


test subjects

medical interface


user background

Cognitive Walkthrough

usability evaluation

HC1, Hörsalsvägen 14
Opponent: Prof. Jan Gulliksen, Kungliga tekniska högskolan (KTH)


Yuanhua Liu

Chalmers, Produkt- och produktionsutveckling


Produktionsteknik, arbetsvetenskap och ergonomi

Hälso- och sjukvårdsorganisation, hälsopolitik och hälsoekonomi

Medicinsk laboratorie- och mätteknik

Människa-datorinteraktion (interaktionsdesign)

Datavetenskap (datalogi)



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 2950

HC1, Hörsalsvägen 14

Opponent: Prof. Jan Gulliksen, Kungliga tekniska högskolan (KTH)

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