Chunk #3 — Development and Heterotypic Continuity of Externalizing Problems — Ensuring statistical equivalence for comparing scores on different measures
Several statistical approaches have been used to increase comparability of measures. One approach is to standardize or age-norm measures across time (e.g., a T- or z-score), which places variables on a standard normal metric. Researchers are often cautioned against standardizing variables in longitudinal designs, however (Stoolmiller, 1995; Willett, Singer, & Martin, 1998). This practice would actually prevent observing changes in means or variances across time because standardization holds them constant.
