KPI · Move higher
Task success rate
Share of users who complete a defined task under the success criteria set before testing.
Task success rate is the basic bottom-line usability measure: did the user complete the task or not? Define the task, allowed paths, and success criteria before the test or analysis.
For affordance hijacking, compare success before and after separating ambiguous controls. A better design should raise completion while lowering accidental stops, discards, deletes, and recovery work.
How patterns use this KPI
| Pattern | How it's instrumented | Why it matters there |
|---|---|---|
| Affordance Hijacking | usability-test or production task completion for affected flows | Semantic mismatch should fall as successful completion rises. |