Chunk #4 — Development and Heterotypic Continuity of Externalizing Problems — Ensuring statistical equivalence for comparing scores on different measures
A more promising approach recommended by Little (2013) for longitudinal designs may be a proportional scoring metric, such as proportion-of-maximum (POM) scoring. POM scoring divides each individual’s score on a measure by the total possible score, rendering the individual’s score a proportion of the maximum possible, with the assumption that similar proportions correspond to similar trait levels. Because all proportions have the same possible range (0–1), they have greater comparability than the raw metric, and unlike standardization, still allow growth over time. Another advantage of POM scoring over standardization in growth curve models is that it does not distort any of the fundamental statistics of the variable to provide a “reasonably comparable scale” (McArdle, Hamagami, Meredith, & Bradway, 2000, p. 60).
