Usability refers to the extent to which a system, product or service can be used by specific users in a specific context of use in order to achieve certain goals effectively, efficiently and satisfactorily. It is thus closely related to the more colloquially common term of user friendliness and the broader concept of user experience (UX). It is a notion close to that of affordance, or even ergonomics which is however broader. The criteria for usability are:
- Efficiency: the product allows its users to achieve the intended result.
- Efficiency: achieves the result with less effort or requires minimal time.
- Satisfaction: comfort and subjective evaluation of the interaction for the user.
In terms of performance characteristics, a distinction is also made between those that are absolutely necessary and those with additional benefits. In the context of the standardized consideration, usability can only ever refer to sufficiently objectifiable facts. The examination of usability, including user-friendliness, are essential components in product tests.
Since medical devices are usually safety-critical devices, special usability requirements must also be imposed on these devices. Thus, in addition to the usability factors of efficiency, effectiveness and satisfaction, safety must also be taken into account. Also, a usability test should be carried out in a special usability laboratory to simulate a typical usage environment and situation.
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While ergonomics is mainly the result of a concern to improve working conditions, usability is closer to quality approaches. These two currents can come together, as usable software is potentially a better tool if it is to be used in a work situation. A system can meet all usability criteria but be useless. It is the adequacy between the activity and the tool that will make it possible to say that this tool is useful. Activity analysis methods allow us to identify which features the application should provide, in other words which features are useful. A system of good ergonomic quality must be both useful and usable.
