Much of this chapter has to do with the statistical technique of factor analysis. It explains this technique in terms of geometry and matrix algebra. Since this is not a book on math, the highlights of this presentation will be presented and discussed in as simple a manner as possible.
Sir Cyril Burt was a medical tester who studied twins, and he made quite a name for himself, publishing papers during his retirement. "The story of Burt's undoing is now more than a twice-told tale. Princeton psychologist Leon Kamin first noted that, while Burt had increased his sample of twins from fewer than twenty to more than fifty in a series of publications, the average correlation between pairs for IQ remained unchanged to the third decimal place -.....
