The Galton Board is a 7.5” by 4.5” desktop probability machine. This device brings to life the statistical concept of normal distribution. As you rotate the Galton Board on its axis, you set into motion a flow of steel beads that bounce with equal probability to the left or right through several rows of pegs. As the beads accumulate in the bins, they approximate the bell curve, as shown by the yellow line on the front of the Galton board. This hands-on Galton Board allows you to visualize the order embedded in the chaos of randomness.

The Galton Board incorporates Sir Francis Galton’s (1822-1911) illustration of the binomial distribution, which for a large number of beads approximates the normal distribution. It also has a superimposed Pascal’s Triangle (Blaise Pascal, 1623-1662), which is a triangle of numbers that follows the rule of adding the two numbers above to get the number below. The number at each peg represents the number of different paths a bead could travel from the top peg to that peg. The Fibonacci numbers (Leonardo Fibonacci, 1175-1250), can also be found as the sums of specific diagonals in the triangle.

When rotated on its axis, the 3,000 beads cascade through rows of symmetrically placed pegs in the desktop-sized Galton Board. When the device is level, each bead bounces off the pegs with equal probability of moving to the left or right. As the beads settle into the bins at the bottom of the board, they accumulate to approximate a bell-shaped curve. Printed on the board are the bell curve, as well as the average and standard deviation lines. The bell curve, also known as the Gaussian distribution (Carl Friedrich Gauss, 1777-1855), is important in statistics and probability theory. It is used in the natural and social sciences to represent random variables, like the beads in the Galton Board.

The Galton Board is reminiscent of Charles and Ray Eames’ groundbreaking 11-foot-tall "Probability Machine,” featured at the 1961 Mathematica exhibit. An even larger Eames probability machine was showcased at IBM’s Pavilion for the 1964 World’s Fair in New York.