The median rank function is used to estimate the cumulative probability of failure of the of identically stressed samples. There are several simple formulas proposed by Weibull and others [1] that give approximate values for the median rank.

The exact median rank function is related to the incomplete beta function , which is hard to calculate. Jacquelin [2] recommends an algorithm based on the Newton-Raphson method.

This Demonstration presents the exact median rank using Jacquelin's method and plots it in different ways.