Conducting Heuristic Evaluations and Severity Ratings

A Heuristic Evaluation is an expert review methodology where 3 to 5 usability specialists independently inspect an interface against Nielsen's 10 heuristics.

Nielsen's Usability Severity Scale

• 0 - Not a usability problem: Does not affect user task completion.
• 1 - Cosmetic problem only: Need not be fixed unless extra time is available.
• 2 - Minor usability problem: Low priority; causes slight user hesitation.
• 3 - Major usability problem: High priority; users experience significant friction or abandonment.
• 4 - Usability catastrophe: Imperative to fix before release; prevents users from completing primary transactions.

Multiple evaluators are essential: 1 evaluator typically finds ~35% of usability defects, while 3 to 5 evaluators uncover 75% to 85% of all problems.