The Galton board (named after Sir Francis Galton), also known as quincunx or
bean machine,
is a statistical device comprised of triangular array of pegs.
The pegs are arranged in staggered order, and a lower half divided into a number of
evenlyspaced rectangular slots.
In the middle of the upper edge, there is a funnel into which balls can be poured.
Balls are dropped onto the top peg and then bounce their way down to the bottom
where they are collected in
rectangular slots. Each time a ball hits one of the pegs,
it bounces either left or right with some probability $p$.
If the number of balls is sufficiently large and when $p=1/2$, then the balls
collected in the slots form
the "bellshaped" curve of the normal distribution.
This applet demonstrates Galton board experiment.
