Galton Board

The bean machine, also known as the Galton Board or quincunx, is a device invented by Sir Francis Galton[1]:63f to demonstrate the central limit theorem, in particular that the normal distribution is approximate to the binomial distribution. A bean machine for the log-normal distribution (common in many natural processes, particularly biological ones), which uses isoceles triangles of varying widths to ‘multiply’ the distance the bead travels instead of fixed sizes steps which would ‘sum’, was constructed by Jacobus Kapteyn while studying & popularizing the statistics of the log-normal in order to help visualize it & demonstrate its plausibility[6]. Denoting the number of rows of pegs in a Galton Board by n, the number of paths to the kth bin on the bottom is given by the binomial coefficient .

Source: en.wikipedia.org