It is not just that a composite score averages the functioning of separate constructs in its association with measures of other constructs. The problem is more severe than that. A second source of uncertainty is that the same composite score will tend to reflect different combinations of construct scores for different individuals in a sample. For example, imagine two individuals with the same overall Neuroticism score on the Revised NEO Personality Inventory (NEO PI-R; Costa & McCrae, 1992) measure of the five-factor model (FFM) of personality. Two of the six facets of Neuroticism in that measure are angry hostility and anxiety. One person could be high in angry hostility but low in anxiety, and the other could be low in angry hostility but high in anxiety. This possibility is not just hypothetical: In the standardization sample, the two traits correlated r = .47, meaning they shared only 22% of their variance (Costa & McCrae, 1992). Thus, covariation of an overall Neuroticism score with another variable lacks clear meaning: The Neuroticism score likely reflects different patterns of traits for different individuals.
