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This study compares a quartimax rotation of the centroid factor loadings for Thurstone's Primary Mental Abilities Test Battery with factorings of the same correlation matrix by Thurstone (simple structure), Zimmerman (revised simple structure), Holzinger and Harman (bi-factor analysis), and Eysenck (group factor analysis). The quartimax results agree very closely with the solutions of Holzinger and Harman and of Eysenck, and reasonably well with the two simple structure analyses. The principal difference is the general factor provided by the quartimax solution. Reproduction of the factorial structure is sufficiently good to justify its use at least as the first stage of rotation. More extensive trial of the method will be needed with more varied data before it will be possible to decide whether quartimax factors meet psychological requirements sufficiently well without further rotation.

A procedure is described for the execution of a principal axes analysis on a computer. Reasons for preferring a principal axes to a centroid solution in the initial factoring of the matrix are given. The University of Illinois electronic computer (Iliac) is then described, followed by an explanation of the sine-cosine method adopted for calculating the factor loadings, and the daily computational procedures for factorizing a correlation matrix once the appropriate set of machine orders is prepared.

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