Design A/B Tests Correctly
Foundations & Process · research
Updated 2026-07-28
- A/B testing measures behavior, not preference.
- Good tests change one meaningful variable:
Example:
- Button placement.
- Copy.
- Flow length.
- Avoid testing:
- Multiple unrelated changes.
- Measure:
- Conversion.
- Completion.
- Retention.
- Errors.
- A winning metric is not always a better experience.
- Optimize for user value, not only clicks.
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UX Handbook