Factor analysis (FA)

Factor analysis (FA) originated in psychometrics as a theoretical underpinning and rationale to the measurement of individual differences in human ability. In 1904, Charles Spearman published his seminal paper (Spearman, 1904), which is considered the beginning of FA. The purpose was to measure the human intelligence, thought at that time to be a single unobservable entity, called general intelligence g. In his paper, Spearman tried to quantify the influence of g on the examinee’s test scores on several topics: Pitch, Light, Weight, Classics, French, English and Mathematics. He used regression-like equations but with the difference that g is not available (observable) as in the regression problems.