Factor analysis
Factor analysis is a statistical test that is used to find relationships between multiple correlated measures and Spearman played a clear part in its development. Spearman coined the term factor analysis and used it extensively in analyzing multiple measures of cognitive performance. It was factor analytic data which led Spearman to postulate his original general and specific factor models of ability. Spearman applied mathematical procedures to psychological phenomena and molded the outcome of his analysis into a theory – which has greatly influenced modern psychology. Factor analysis and its modern relations confirmatory factor analysis and structural equation modelling underlie much of modern behaviour research.