Corrections
On the top of page 330, there is an error in the formula. Where there is (k - 3) there should be 1/(k - 3). Thanks are due to Oliver Lüdtke.
On page 335, the fifth line of the last paragraph, there is a missing word of "be." It should read be "would also be distinguishable." Thanks are due to Larry Kurdek.
Elaborations
A paper by Edwards (Edwards, J. R. (1995). Alternatives to difference scores as dependent variables in the study of congruence in organizational research. Organizational Behavior and Human Decision Processes, 64, 307-324. See also Griffin, D., Murray, S., & Gonzalez, R. (1999). Difference score correlations in relationship research: A conceptual primer. Personal Relationships, 6, 505-518.) describes a strategy to empirically select whether one should compute a discrepancy or difference score.
