Binomial Test

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About this app

Binomial Test — is your proportion really different from the claim?

You flipped a coin 50 times and got 36 heads. Is the coin fair, or is 36 too many to be luck? Binomial Test answers exactly this kind of yes/no question: you have k successes out of n trials, and you want to know whether the true success rate really differs from a claimed value p0. No data lists, no guesswork — just the counts, computed exactly.

Everything runs offline on your device. Nothing is uploaded.

WHAT IT DOES
• Exact binomial test — the p-value is computed exactly (not a normal approximation), so it stays accurate even for small samples.
• One-sided and two-sided — ask "is p different from p0?", "is it greater?", or "is it less?".
• Wilson 95% confidence interval — a reliable range for the true proportion; if it excludes p0, the result is significant.
• Observed vs expected — see your proportion p-hat next to the claimed rate at a glance.

EASY, FLEXIBLE INPUT
• Type the exact numbers, or drag the slider — your choice.
• Handy minus / plus stepper buttons for quick one-at-a-time adjustments.
• Pick successes k, trials n and the claimed probability p0 in seconds.

CLEAR VISUALS
• Binomial PMF bar chart with your observed count highlighted and the rejection region shaded — you can literally see the p-value add up.
• Proportion-and-confidence-interval line showing p-hat, the interval, and the claim p0 together.
• Beautiful, distraction-free "cranberry" design.

LEARN THE CONCEPT
• Plain-language explanations of the binomial setup, the exact p-value, and confidence intervals.
• Crisp mathematical formulas rendered with KaTeX — fully offline, never overlapping or cut off.

COIN-FLIP SIMULATOR
• Rig a coin's true bias, flip it n times, and test it for fairness.
• See for yourself why a slight bias is hard to catch with few flips but easy with many.

WORKED EXAMPLES
• Is the coin fair? (36 of 50)
• A free-throw claim of 80% — but only 33 of 50 made.
• A factory defect target of 5% vs 16 defects in 200.

WHO IT IS FOR
• Students learning statistics and hypothesis testing.
• Teachers who want a clean, visual demonstration.
• Anyone who needs a quick, exact binomial test on the go.

Small, fast, offline, and ad-supported. Download Binomial Test and find out whether your result is real or just chance.
Updated on
Jun 16, 2026

Data safety

Safety starts with understanding how developers collect and share your data. Data privacy and security practices may vary based on your use, region, and age. The developer provided this information and may update it over time.
This app may share these data types with third parties
Device or other IDs
No data collected
Learn more about how developers declare collection
Data is encrypted in transit

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Binomial Test