Exercise 3: Why "5 Users" and "5 Experts" Are Not the Same Thing — Possible Solution ==================================================================== This is incorrect because the shared number 5 is genuinely a coincidence of scale, not a sign the two methods are measuring the same thing. Chapter 2's "5 users" refers to real people, unfamiliar with the interface, actually attempting real tasks - what gets measured is real behavior: where people hesitate, get confused, or fail a task. This chapter's "3-5 evaluators" refers to UX experts independently reviewing the interface against a fixed checklist of 10 established heuristics - what gets measured is expert judgment applied systematically, not real behavior from real, unfamiliar users at all. Because the two methods measure fundamentally different things, they also catch fundamentally different kinds of problems. A heuristic evaluation can quickly catch a violation of an established pattern (inconsistent labeling, poor error messages) without needing any real users at all - but it structurally cannot reveal a problem born from actual user context or motivation, the kind of thing only real behavior can expose. Treating the two as interchangeable because they happen to share a similar headline number would mean skipping real user research on the mistaken assumption that expert review alone already covers the same ground. ANSWER: This is incorrect - the two numbers happening to be similar in size is a coincidence, not evidence the methods are equivalent. "5 users" measures real behavior from real, unfamiliar people attempting real tasks; "3-5 evaluators" measures expert judgment against a fixed checklist, with no real users involved at all. Each method catches real problems the other one structurally cannot, which is exactly why one can't substitute for the other. WHY THIS WORKS AS AN ANSWER ------------------------------ This correctly explains that the shared number is coincidental rather than meaningful, and specifies exactly what each method actually measures and what each one structurally misses, rather than simply asserting the two are different without explaining why.