\input zb-basic \input zb-matheduc \iteman{ZMATH 2013b.00788} \itemau{Deakin, Michael} \itemti{History of mathematics: the vectors of mind.} \itemso{Parabola 48, No. 2, 14-26 (2012).} \itemab From the editorial: The article continues the author\rq s History of mathematics series. In this article he considers factor analysis applied to test scores. The underlying idea in factor analysis is to determine if a number of observables $y_1,y_2,\dots ,y_n$ can be linearly related to a smaller number of unobservable factors $f_l,f_2,\dots ,f_k$. For example the observables might be scores from many different students in $n$ different tests. \itemrv{~} \itemcc{K80 A30 H60} \itemut{cognitive psychology; intelligence factors; factor analysis; principal component analysis; vectors; descriptive statistics; means; variance; standard deviation; correlation coefficient; correlation matrices; matrix of covariances; characteristic polynomials; eigenvectors; largest eigenvalue; objective evidence; subjective evidence; fundamental factors; objective factors; subjective factors} \itemli{} \end