RandJoy
Normal distribution generator
Explore a bell-shaped distribution, one reproducible sample at a time.
Latest result
Ready when you are
Explore a bell-shaped distribution, one reproducible sample at a time.How it works
- Set the center (mean) and spread (standard deviation). Both describe the model, not a promise about one sample.
- Choose up to 1,000 values and a seed. Generate to see a histogram, sample mean and sample standard deviation.
- Export all values or the recipe. Keep the seed to repeat the experiment, or choose New seed to compare another sample.
A model with a center and a spread
RandJoy transforms versioned pseudorandom draws using the Box–Muller method, then reports values to six decimal places. A standard normal model has mean 0 and standard deviation 1. Small samples can look uneven and their mean need not be exactly zero. The implementation uses finite-precision arithmetic and a finite random source, so it does not generate mathematically unbounded tails. These are educational and software-testing samples.
Your inputs stay with you
Your inputs and generated results stay in this browser. Settings and five recent runs use local storage; clearing browser data removes them. Export a copy to keep it. Hosting may record standard page-request logs, but generated rows and participant names are not sent to the server.
Why does the histogram change?
A histogram counts observed samples in intervals. Different seeds produce different observations, even with the same model. More observations often make the overall shape easier to recognize, but do not force an exact curve. The table and export contain the values used in the preview.
Repeatable test data
The research tools use the versioned xoshiro128** pseudorandom generator with named seed streams. They are intended for small examples and testing, not secrets or certified draws. A recipe records parameters and generator version. Floating-point transforms are rounded to six decimal places; keep exported files when exact cross-platform bytes matter.
Seeds are repeatable. Use the password generator for credentials.