1. A method for quantifying a difference between a first population distribution data set and a second population distribution data set, the method comprising: using a machine computational module, mapping a population stability index to a population distribution difference function; using the machine computational module, evaluating the population stability index based on the mapping, the first population distribution data set and the second population distribution data set; using a receiver in electronic communication with the computational module, receiving a population stability index critical value corresponding in the mapping to a population distribution difference function value; storing the population stability index value in machine readable memory; and using the machine computational module, comparing the critical value to the population stability index based on the first population distribution data set and the second population distribution data set.