Concepts

Questions answered here

• What sample size is required for formative and summative human factors studies?Sample size depends on your research method and objectives. Formative evaluations typically require five to eight participants per user group to detect frequent usability issues. For summative validation studies, the FDA usually looks for at least fifteen participants per user group. Broader methods like surveys or workflow observations require sample sizes matched to the specific research question.
• What are affordances in medical device design?Affordances are design clues indicating how a device should be used, showing users what to press, pull, connect, or hold. They can be physical, visual, tactile, auditory, or digital. Effective affordances guide users directly at the point of use, reducing uncertainty and preventing potential harm without relying heavily on instructions.
• Why is plain language important in medical device labelling?Plain language ensures instructions, warnings, and interface text are easily understood and actionable without sacrificing accuracy. Because users may be stressed, tired, or in pain, complex terminology increases the risk of use error. Clear communication reduces cognitive effort, supports safe device use, meets regulatory expectations, and builds user confidence.
• Why is managing cognitive load critical in medical device design?Cognitive load is the mental effort required to operate a device. Working memory holds only three to five items, and exceeding this capacity leads to overload and mistakes. High cognitive load causes eighty per cent of medical device user errors. Designers reduce this risk by removing unnecessary steps, simplifying instructions, and providing clear visual cues.
• Why are mental models important in medical device design?A mental model is the user's internal picture of how a system works. In medical device design, matching the layout, feedback, and behaviour to this model helps users predict outcomes and execute operational sequences accurately. Designing around the user's mental model provides essential safety, predictability, and confidence during real-world device use.
• Why is design consistency important in medical device interfaces?Design consistency in medical devices ensures symbols, colours, and interface cues behave predictably, allowing users to operate without unnecessary cognitive load. Inconsistent design forces users to question visual cues, increasing the risk of error. Changes to established conventions must be intentional and evidence-based, as confusion is dangerous in high-risk environments.