| name | usability-evaluation |
| description | Use when auditing an existing interface for usability issues, when running a heuristic evaluation or cognitive walkthrough, when scoring an SUS survey, or when prioritizing UX bugs by severity. |
| metadata | {"references":["references/nielsen-heuristics.md","references/scoring-methods.md","references/walkthrough-guide.md"]} |
Usability Evaluation
Heuristic evaluation workflow
- Recruit 3-5 evaluators with UX knowledge (returns diminish past 5).
- Each evaluates independently against Nielsen's 10 heuristics — record screen, heuristic, description, severity, fix.
- Merge — dedupe, average severity.
- Calibrate — evaluators review each other's severity ratings together; resolve disagreements > 1 point. Goal: inter-rater agreement on severity within ±1.
- Prioritize and report — sort by severity desc; deliver top issues with screenshots + fixes.
Pass/fail gates before sign-off:
- All severity-4 issues have an owner and a fix landing this release.
- No severity-3 issue is "won't fix" without explicit product approval.
Nielsen's 10 heuristics (cheat sheet)
- Visibility of system status
- Match between system and real world
- User control and freedom
- Consistency and standards
- Error prevention
- Recognition rather than recall
- Flexibility and efficiency of use
- Aesthetic and minimalist design
- Help users recognize, diagnose, and recover from errors
- Help and documentation
Full descriptions: nielsen-heuristics.md.
Severity scale
| Rating | Label | Definition | Action |
|---|
| 0 | Not a problem | Disagreement; not a usability issue | None |
| 1 | Cosmetic | Noticed but doesn't affect task | Backlog |
| 2 | Minor | Slows user; can still complete | Next iteration |
| 3 | Major | Significant difficulty; some fail | Before next release |
| 4 | Catastrophe | Cannot complete task | Immediate |
Finding template (use this exact format)
ID: HE-018
Screen: Checkout > Shipping Address
Component: AddressForm
State: Empty / first-load
Heuristic violated: H5 (Error prevention) + H9 (Help recover from errors)
Description:
The ZIP code input accepts arbitrary characters and the form does not
validate until submit. Users entering letters or short ZIPs see the
generic top-of-form error "Please fix the highlighted fields" with no
indication that ZIP is the culprit. Screenshot: see Fig. 18 — error
banner is 3 viewports above the failing field on mobile.
Severity: 3 (Major)
Frequency: occurs to every user with input error · Impact: high
Persistence: until user finds the right field
Recommended fix:
1. Apply inputmode="numeric" pattern="\d{5}(-\d{4})?" maxlength="10".
2. Validate on blur; show inline error directly under the field.
3. Auto-scroll to first invalid field on submit.
4. Replace generic banner with specific message ("ZIP code must be 5 digits").
Effort: S (frontend only) · Owner: TBD
Cognitive walkthrough (4 questions per step)
Inputs: user goal, action sequence, expected experience level.
For each step, answer:
- Q1: Will the user try to achieve the right effect? (Is this step's purpose clear?)
- Q2: Will the user notice the correct action is available? (Visible? Looks interactive?)
- Q3: Will the user associate the action with the desired effect? (Label/icon clear?)
- Q4: Will the user see progress after acting? (Feedback present?)
Any "no" = a usability finding. Document step number, failed question, recommendation. Full method: walkthrough-guide.md.
SUS quick reference
Administer the 10-item SUS questionnaire post-task. Score:
- Odd items: score − 1
- Even items: 5 − score
- Sum × 2.5 = SUS score (0-100)
Benchmarks: < 50 unacceptable · 50-67 marginal · 68 industry avg · 68-80 good · 80-90 excellent · > 90 best-in-class.
Full questionnaire, alternative scales (SEQ, NASA-TLX, SUPR-Q), scorecards: scoring-methods.md.
When to use which method
| Goal | Method |
|---|
| Quick sweep of any screen | Heuristic evaluation (2-4 hrs, 3-5 evaluators) |
| Onboarding / first-time UX | Cognitive walkthrough |
| Benchmark perceived usability over releases | SUS survey post-test |
| Per-task difficulty | Single Ease Question (SEQ) |
| Validate suspected issues with real users | Moderated usability testing (5-8 participants) |
Next Steps
