Updated: 31 October 2026

Plan an A/B test properly

This prompt helps you plan an A/B test on what you are testing, given the current performance and your traffic.

text-ab-test-plan — chatgpt — 53 words

Help me plan an A/B test on [WHAT I AM TESTING].

Current performance: [BASELINE METRIC]
Traffic per week: [VISITORS]
Change I want to test: [CHANGE]

Write the hypothesis, the primary and guard-rail metrics, the sample size or duration needed, how to split traffic, common mistakes to avoid and how to decide the result.

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Decide the success metric and sample size before you look at any results.

Get a better result

What you will get

A test plan with a hypothesis, a primary metric and guard-rail metrics, the sample size or duration, how to split traffic, common mistakes and a clear rule for deciding the result.

Why it works

Most A/B tests fail before they start, from no clear hypothesis, too little traffic or peeking at results. The prompt asks for each piece up front: the hypothesis, a primary metric with guard-rail metrics, the sample size or duration from your real traffic, and how you will decide. Listing common mistakes makes the plan defensive, and the tip is the key rule: decide success before you look.

Common mistake

You stop the test as soon as one side looks ahead.

Fix: Set the sample size or duration first, as the tip says, and wait until it ends.

Also watch for

You change two things at once. Test one change so you know what caused the result.
The traffic is too low for the effect. Give the real weekly visitors and baseline, and accept if the plan says the test needs longer or a bigger change.

Try a variation: make a results template

Ask for a one-page template to record the result, the size of the change, any surprises and what you will test next.

Still not right? Reply with this

Write the hypothesis and the decision rule as two sentences I can share with the team before the test starts, plus the exact end date based on my traffic.