Beyond the Quintessential Quincunx

The quincunx, a contraption with balls rolling through a triangle-shaped arrangement of nails, was invented to illustrate the binomial distribution and the central limit theorem for Bernoulli random variables. As it turns out, a modification of the quincunx can be used to teach many different concepts, including the central limit theorem for independent but not identically distributed random variables, permutation tests in a paired setting, and the generation of a random variable with an arbitrary continuous distribution from a uniform variate. This article uses a universal quincunx—“uncunx”—applet to illustrate these and other applications.