During a usability test, a participant repeatedly taps the wrong button when trying to submit a form. According to UCD principles, how should this be interpreted?
AThe participant lacks sufficient technical literacy to use the interface
BThe test should be discarded because the participant is an outlier
CThe design has a flaw — usability failures are always design failures, not user failures
DThe button label should be translated into simpler language for less-educated users
UCD holds that usability failures are always design failures. If a user takes the wrong action, the design failed to make the correct action clear, discoverable, or easy. Blaming user literacy or treating the result as an outlier ignores the diagnostic value of the observation. The first step is to understand why the wrong button was chosen, not to defend the existing design.
Question 2 True / False
In user-centered design, the correct solution is usually found by simply asking users what they want and building exactly that.
TTrue
FFalse
Answer: False
Users report symptoms and desires, not solutions. Henry Ford's famous (apocryphal) observation — 'If I'd asked people what they wanted, they would have said faster horses' — captures a real UCD truth: users describe their current experience and immediate frustration, not the design space of possible solutions. The designer's job is to synthesize user needs into solutions users couldn't have specified themselves. UCD means centering the user's needs, not outsourcing design decisions to them.
Question 3 Short Answer
Why does usability testing with only five participants reveal approximately 80% of usability issues, rather than requiring large sample sizes like quantitative research?
Think about your answer, then reveal below.
Model answer: Because usability problems are patterns, not rare events — if a design flaw exists, most users will encounter it. Each new participant surfaces diminishing returns of new issues after the first few, since the same problems recur across users.
Nielsen's research on diminishing returns in usability testing shows that the first user reveals the most new issues, the second reveals fewer new ones, and by the fifth, nearly all major patterns have appeared. This is different from quantitative research measuring effect sizes, where large samples are needed for statistical precision. Usability testing is qualitative pattern detection: five participants is enough to find what is broken, though not enough to measure how broken it is across a population.