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The Normal Share of Paupers

In 2009, China began regional pilot programs that repurposed credit scores to a broader purpose – scoring a person’s “social credit.”  100 years earlier, at the height of the eugenics craze, the famous statistician Francis Galton undertook to repurpose statistical concepts in service of social engineering. The starting point was a social survey of LondonContinue reading “The Normal Share of Paupers”

Purity

In classification, purity measures the extent to which a group of records share the same class.  It is also termed class purity or homogeneity, and sometimes impurity is measured instead.  The measure Gini impurity, for example, is calculated for a two-class case as p(1-p), where p = the proportion of records belonging to class 1. Continue reading “Purity”