Two-proportion Experiment Power Planner

How to use Two-proportion Experiment Power Planner

Cohen h=2asin√pB−2asin√pA. A normal shift |h|√(nA*nB/(nA+nB)) with the selected critical tail approximates power. Planning searches whole nA and exact-decimal ceiling nB under your allocation ratio.

1. Enter assumed control rate, assumed variant rate, type-i error fraction, target power, group b/a allocation ratio, group a count for achieved-power mode.
2. Choose the stated convention and check the units and supported model.
3. Calculate, inspect the result, then copy or download it.

Good to know

• User rates strictly between0 and1, alpha.0001–.2,power.5–.999,plain-decimal ratioB/A.1–10,groups at most1billion. Each modeled expected success/failure count must be at least5. Approximation only; no sequential peeking or guaranteed lift.
• Runs locally. Text/JSON fields are capped at30,000 characters; stricter page-specific and numeric-string limits also apply. Numeric inputs are bounded to magnitude1e15 and nonzero magnitude at least1e-100 unless an exact-string mode states otherwise. Approximate summaries use12 significant digits; CSV numeric cells retain the complete stored value and potentially formula-like string cells gain a protective apostrophe; unsupported, non-finite or detected underflow states return an error.