A set of mathematical and statistical techniques for the analysis of a set of observed or manifest variables (M) in terms of a smaller set of unobserved or latent variables (K<M). Charles E. Spearman (1863-1945) is generally acknowledged with devising the technique as a consequence of discovering positive correlations among seemingly unrelated scores derived from tests administered to school children. His solution led him to propose a general mental ability (g) underlying intelligence.
See Confirmatory factor analysis (CFA), Construct equivalence, Crystallized intelligence, Discriminant validity, Exploratory factor analysis (EFA), Factor loadings, ‘g’, Latent factor/score/variable, Measurement invariance