Introduction to A/B testing
Your roadmap for this lesson
- How an A/B test works
- The six steps of a sound test
- Mistakes that ruin test results
Short answer
An A/B test shows two versions of a page to similar users at the same time and measures which converts better. Start with a hypothesis, change one main element, split traffic randomly, and run until you reach enough sample size and statistical significance. Then roll out the winner and record what you learned.
Six steps
- Form a hypothesis: “Showing shipping cost on the product page will raise add-to-cart rate because users fear hidden fees.”
- Create versions: A (control) and B (variant), changing one main element.
- Split traffic randomly.
- Run long enough: enough sample size and at least one full business cycle (usually 2 or more weeks).
- Check significance: commonly 95% before declaring a winner.
- Implement and document the winner and what you learned.
Common mistakes
- Stopping early because one version looks ahead after two days.
- Testing too many changes at once, so you cannot tell what worked.
- Ignoring segments: a winner on desktop may lose on mobile.
Quick quiz
Your action
Key terms
- A/B test
- A comparison of two versions with split traffic.
- Control
- The original version, A.
- Variant
- The changed version, B.
- Statistical significance
- Confidence that a result is not due to chance.
Questions beginners ask
How long should a test run?
At least one full business cycle, usually two weeks or more.
What if my site has little traffic?
Test bigger changes, or use surveys and recordings instead.
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