The Tetrad Difference Criterion

Abstract

IN recent years the quantity F, called the ‘tetrad-difference’, has become very important in psychological investigations as to the possible nature of the underlying causes of mental activities. If there are four such activities, and r₁₃, r₂₄, etc., the six correlation coefficients, F is defined by the equation F = r₁₃r₂₄ – r₁₄r₂₃. The value of F, in practice, approximates to zero.