{"id":"mkt2-ab-test-plan-sample-days","audience":"product-managers","category":"planning","track":"marketing","technique":"constraints","level":"advanced","title":"Write an A/B test plan with sample size and run time worked out","free":false,"task":"You're planning a test on the pricing page headline. Write a prompt for exactly six plain-text lines labeled Hypothesis:, Change:, Primary metric:, Sample per variant:, Days to run: and Stop rule:. Days to run shows the math from the daily traffic split between two variants, then rounds up to whole weeks. Under 100 words, and no test of anything beyond the one change.","materialLabel":"Test inputs (attached to your prompt automatically)","material":"TEST PLAN INPUTS - pricing page headline\n\nCurrent headline: \"Plans that fit your team\". Proposed: \"Start free, upgrade when you grow\".\nGoal: increase free signups from the pricing page. Primary metric: signups per visitor to the pricing page.\nSample size calculator result: 10,000 visitors per variant needed.\nTraffic: about 1,250 visitors a day to the pricing page; split 50/50 between two variants.\nTests in this team must run in whole weeks (to cover weekday patterns).\nThe designer also wants to change the button color and add a testimonial in the same test. (Not part of this plan.)\nSecondary metrics to watch but not decide on: bounce rate, time on page.\nThe VP wants to stop the test as soon as one variant is ahead.","rules":[{"type":"plainText"},{"type":"maxWords","max":100}],"mistakes":[{"title":"Stopping when ahead","why":"The AI follows the VP's wish.","fix":"Say: \"Stop rule: run the full sample and whole weeks.\"","checks":["r2"]},{"title":"Bundling extra changes","why":"The AI adds the button color and testimonial.","fix":"Say: \"One change only: the headline.\"","checks":["r2"]},{"title":"Forgetting to round to weeks","why":"The AI says 16 days.","fix":"Say: \"Show the math, then round up to whole weeks.\"","checks":["r1"]},{"title":"Missing labels","why":"The AI writes a narrative plan.","fix":"List the six labels.","checks":["r0"]},{"title":"Letting markdown through","why":"AI adds bold text and headings by default.","fix":"Add: \"Plain text only, no bold, no headings.\"","checks":["plainText"]},{"title":"Trusting the AI to count words","why":"AI is bad at counting and often runs past a word limit.","fix":"Cap each part (for example \"each line under 15 words\") so the total lands well under the limit.","checks":["maxWords"]}],"promptHints":[{"label":"Lists the six labels","patterns":["hypothesis:.*change:.*primary metric:.*sample per variant:.*days to run:.*stop rule:"]},{"label":"Shows the days math","patterns":["625","per variant per day","show the math"]},{"label":"Rounds to weeks","patterns":["whole weeks","round"]},{"label":"Limits to one change","patterns":["one change","only the headline","headline only"]},{"label":"Sets the stop rule","patterns":["full sample","not (to )?stop","stop rule"]}],"hint":"A plan is credible when the days are worked out and the stop rule resists peeking. Give the labels, the math and the one-change limit.","mission":"Plan a pricing-page headline test and work out how long it runs.","musts":["Show days math","Round up to weeks","Test one change only"],"rubricLabels":["The output has exactly six lines starting Hypothesis:, Change:, Primary metric:, Sample per variant:, Days to run: and Stop rule:","Primary metric is signups per pricing-page visitor, Sample per variant is 10,000, and Days to run shows 10,000 / 625 = 16 days rounded up to 21 days (3 weeks)","Change covers only the headline (not the button color or testimonial), and Stop rule says to run to the full sample and whole weeks, not to stop when one variant leads"]}