Invented by Sir Francis Galton in 1894, the Galton board (or quincunx) drops balls through a grid of pegs. At each peg a ball goes left or right with equal probability. After many rows the balls collect into bins, forming a bell curve—a physical proof of the central limit theorem.
This board is rigged. A slow pendulum tilts the frame left and right, biasing the odds at every peg. The result is a distribution whose skewness oscillates: when tilted right, balls cluster left with a long right tail; when tilted left, the mirror image.
Watch the three markers diverge: in a skewed distribution mode ≠ median ≠ mean. The mode tracks the peak, the mean chases the tail, and the median splits the difference—a signature of asymmetry.
