At each peg inside a Galton board, a marble has a roughly equal chance of bouncing left or right. After many such bounces, those tiny random deflections add up. Drop 200 marbles and something predictable emerges: about 50% land in the two center slots, and the overall spread forms a bell curve — a pattern you can predict before a single marble falls.

Release 200 marbles from a funnel at the top of a pegboard and let them fall into 12 compartments along the bottom. Counting how many land in each slot gives you a frequency distribution — a picture of which results happen often and which happen rarely. About 50% end up in the two center slots, a pattern that emerges from the structure of the device itself.

A pegboard device puts normal distribution on display. You drop 200 marbles through a grid of wooden dowels that deflect each marble randomly left or right. About 50% land in the two center slots, while only 16% reach the two outermost slots on each end. Each random bounce adds up across many rows, and the combined effect pushes most marbles toward the middle. The pattern repeats within 5% on every trial — and the results form a bell curve, the defining shape of a normal distribution.