Skip navigation

Galton Board

Galton Board or bean machine (also known as the quincux) is a device invented by Sir Francis Galton to demonstrate the central limit theorem, in particular, the fact that the normal distribution is approximate to the binomial distribution.

The machine consists of a vertical board with interleaved rows of pins. Balls are dropped from the top, and bounce either left or right as they hit the pins. Eventually, they are collected into one-ball-wide bins at the bottom. The height of ball columns accumulated in the bins will eventually approximate a bell curve, the curve of a normal distribution.