Regression to the Mean

This chapter focuses on two events that started the transformation to a quantifying worldview for the general public: (1) developments in transportation, especially the invention of the train (meaning people and goods could travel further) and (2) the consequent tremendous economic expansion which led to a full-blown industrial revolution, first in England and then in America. Work by Charles Darwin showed the broadening impact of quantitative thinking on the discipline of sociology. The chapter also discusses the accomplishments of Francis Galton, including his landmark work Hereditary Genius, the invention of Galton’s bean machine (“quincunx”), which demonstrated the central limit theorem, and his Anthropometric Laboratory, which he set up at the International Health Exhibition to measure mental faculties. Galton also discovered the concept of correlation and “reversion to the mean,” evolving the latter into “regression to the mean,” and invented many other statistical concepts, such as quartile, decile, and ogive.