Heuristic evaluation is deliberately done by several evaluators working independently, because any single person catches only a fraction of the usability problems in an interface. That design choice creates a follow-up task: once everyone has finished inspecting on their own, the separate lists of findings have to be combined into one clean, agreed-upon set of problems that a team can actually act on. That combining step is called aggregation.
Aggregation usually happens in a structured meeting. Evaluators walk through their findings one at a time, merge duplicates that were described in different words, decide whether two similar observations are really one underlying problem or two distinct ones, settle which heuristic each violation maps to, and negotiate a single severity rating when individual ratings disagree. The output is a deduplicated, prioritized problem list with enough detail (location, heuristic violated, severity, suggested fix) for designers to use.
As you watch the videos below, pay attention to two things. First, how the evaluation process is structured from the start, since consistent note-taking and clear problem descriptions during individual evaluation are what make deduplication possible later. Second, how small numbers of evaluators or test users can still produce trustworthy, decision-ready conclusions — the same logic that justifies why we aggregate across a handful of evaluators rather than relying on one.
A short walkthrough from Nielsen Norman Group on how to run a heuristic evaluation systematically: reviewing the interface against a set of heuristics, recording the problems found, and working through the product in an organized way. Expect it to cover the roles of multiple independent evaluators and how their individual findings feed into a combined set of results.
It comes from the group that originated the method, and it frames the full process end to end — which is exactly where aggregation fits, immediately after individual evaluations are complete.
This video addresses the common objection that a small number of participants cannot represent all users, and explains how limited-scale usability work still supports sound business decisions. It discusses what small-sample findings can and cannot tell you, and how to reason about risk when acting on them.
It directly supports the "why aggregation is necessary" subtopic: the value of combining a few evaluators' or users' findings rests on understanding why small samples surface most of the important problems, and it gives you language for defending a merged problem list to stakeholders.
Together these videos reinforce the practical side of the module. The heuristic evaluation walkthrough supports MO2 by showing how violations are identified and recorded against Nielsen's principles (MO1), and it sets up the aggregation step where those individually classified violations are merged into one list. The small-sample video supports MO3 and the negotiation of severity by explaining why findings from a handful of evaluators are credible enough to prioritize and act on, which is the reasoning behind assigning agreed severity ratings and recommending specific fixes.
These videos were chosen from YouTube on October 3, 2026. Each has captions; the player turns them on. Videos on YouTube can be changed or removed — if one no longer plays, tell your instructor. If a player does not appear, use its Watch on YouTube link.