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Sample Size and Duration Estimate in Plain Language

Table output

Understand how much traffic a test needs.

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[VERIFY] is an editorial flag, not a blank to fill. Wherever the prompt shows [VERIFY], check that item against a reliable source before you use it.

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Explain sample size for my test. Baseline conversion rate: [BASELINE_RATE]. Smallest improvement worth detecting: [MINIMUM_EFFECT]. Weekly visitors: [WEEKLY_VISITORS]. Confidence and power I will use: [CONFIDENCE_AND_POWER].

Explain in plain words why small improvements need many visitors. Use a rough formula for two proportions and show an example calculation with my numbers, labelled as approximate, and tell me to confirm with a calculator [VERIFY]. Convert to duration in full weeks.

Return the estimate, a table showing how the required sample changes if the minimum effect is half or double, and advice if the test would take too long: test a bigger change, use a higher-traffic page or choose a different metric.

Add an invented table: baseline 5 percent; to detect an absolute lift of 1 point you may need several thousand visitors per variant; to detect a lift of 0.5 points about four times as many. Present it as an illustration and tell me to confirm with a trusted calculator [VERIFY]. Explain the trade-offs between confidence level and power in a sentence each, without technical jargon.

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