ON EXTENSION ANALYSIS AND ITS RELATION TO CORRELATIONS BETWEEN VARIABLES AND FACTOR SCORES
John Louis Horn · Multivariate Behavioral Research · 1973
Given the intercorrelations among variables that are factored (core variables) and variables that are excluded from a factor analysis (extension variables), matrix algebra algorithms are developed for obtaining the correlations between the extension variables and the factor scores that would be computed by what is called the direct method for obtaining factor scores. The equations needed to obtain such extension analysis results are provided for the case of oblique factors and when either the primary factor or reference vector method of rotation is used.