> Preserved source method from `amplifier-bundle-ergonomics` at `8a6b9a0a5189b5572ea5d5c933f7956227a711fb`. Original examples and runtime claims are historical; the canonical entry point defines current scope.

---
name: usability-study-design
description: Design the lightest valid usability study for a product decision, with explicit population, tasks, measures, analysis, stopping rule, and inference boundaries.
---

# Usability study design

Specify:

1. Decision and hypotheses.
2. Target population and meaningful variation.
3. Realistic tasks, states, environment, and prototype fidelity.
4. Success, critical-error, assistance, abandonment, and quality definitions.
5. Behavioral and supporting subjective measures.
6. Moderation, counterbalancing, instrumentation, and accessibility needs.
7. Analysis plan and stopping rule.
8. What the study can and cannot generalize.

Small formative studies can identify severe breakdowns but do not estimate population prevalence. Questionnaires support behavioral evidence; they do not replace it.