A representative user (plural: representative users) is a person whose characteristics, abilities, experience, and limitations make them a suitable stand-in for an intended user group of a medical device; the selection must also fit the tasks and use contexts under study. In usability engineering, representative users are involved to gain insights into use and to demonstrate that the intended users can use the product safely and as intended. The term follows the intended purpose (intended use) of the device, that is, what the manufacturer specifies it is for.
In this context, representativeness does not mean statistical representativeness of the general population but refers to the user-related characteristics that are relevant for safe use.
Role in the usability engineering process
Selecting representative users is a key prerequisite for valid results from context analyses, formative evaluations, and summative evaluations. Findings from tests with non-representative participants can mask relevant use risks or overestimate the actual usability. The characteristics of the intended user groups are already described in the use specification (German: Anwendungsspezifikation) and form the basis for selecting suitable participants.
Derivation from the use specification
Representative users are derived from the intended user groups of the product. Relevant factors include professional qualification, experience with comparable products, expertise, level of training, age, motor abilities, sensory abilities, and cognitive prerequisites. For home use, patients, family members, or lay persons can also constitute separate user groups.
Representativeness is not uniformity
A common misconception is that all participants in a study should be as similar as possible. In fact, relevant differences within a user group must be taken into account. For example, experienced intensive care nurses and occasional users of the same device can exhibit different risk profiles. People with relevant characteristics, such as particularly little experience or an intended physical limitation, are not mere edge cases if these characteristics are part of the intended user population.
Role in formative evaluations
In early development phases, representativeness can be handled more pragmatically. Formative evaluations primarily serve to identify use problems and to assess design ideas. Even so, test participants should already have the essential characteristics of the target users. Otherwise, there is a risk that critical use difficulties remain undetected.
Requirements in summative evaluations
For summative evaluations, representativeness is especially critical. Participants must credibly reflect the actual user groups of the product, because the study is meant to show that the remaining use-related risks are adequately controlled. The FDA explicitly expects validation participants to be selected so that they are representative of the intended user groups.
Typical mistakes in practice
A common mistake is recruiting readily available people instead of the actual target group, for example development staff, clinical experts with an unusually high level of experience, or non-representative test persons from recruitment panels. Looking only at demographic characteristics while disregarding use-relevant attributes such as experience, training, or physical limitations is also problematic. Such weaknesses can be challenged critically in regulatory reviews.
Regulatory reference
IEC 62366-1 requires, within the usability engineering process, the identification of intended user groups and the consideration of their characteristics in the use specification and the evaluation activities; the selection of representative users follows directly from this requirement. In its human factors guidance, the FDA requires that participants in human factors validation studies represent the intended user groups of the product. It describes a wide range of user-related characteristics that can be relevant for safe use, such as education, experience, physical and cognitive abilities, health status, and language skills. Under ISO 14971, use-related hazards and errors must be considered in risk management; identifying the relevant user groups therefore directly influences the use-related risk analysis. The EU Medical Device Regulation (MDR) does not explicitly use the term "representative users" but relies on the same basic principles for its requirements on intended users and human factors.
Representativeness is not measured by demographic similarity but by the use-relevant characteristics of the intended user groups. Anyone who relies on readily available instead of truly representative participants in formative and especially summative studies risks systematically overlooking safety-relevant use problems.
Frequently asked questions (FAQ)
Do representative users have to be statistically representative of the general population?
No. In usability engineering, the focus is on representativeness with regard to use-relevant characteristics. What matters is reflecting the safety-relevant properties of the intended user groups.
May internal employees be used as representative users?
They are not automatically excluded, but they are often unsuitable if they have non-representative product knowledge, were involved in the design, or know the study objective. Their suitability must be assessed and documented using the same inclusion and exclusion criteria, taking possible bias into account.
Can clinical experts represent ordinary users?
Not automatically. Experts often have different mental models, working methods, and error patterns than occasional users or lay persons.
Must every identified user group be represented in a summative evaluation?
Every intended user group must be considered in the usability engineering process. Whether it must take part in the summative evaluation as a separate group depends on its tasks, the user interface used, and relevant differences from other groups. Omitting or combining groups must be justified in a traceable, risk-based manner.
Do you want to recruit representative user groups for your usability studies in a targeted and regulatorily robust way? We support you with the recruitment of healthcare professionals and patients for your usability tests.
More about our recruitmentSources
- IEC 62366-1:2015+AMD1:2020, Medical devices, Part 1: Application of usability engineering to medical devices
- ISO 14971:2019, Medical devices, Application of risk management to medical devices
- Regulation (EU) 2017/745 on medical devices (MDR)
Related terms
- Formative usability evaluation
- Summative usability evaluation
- Context of use
- User profile