A second practical challenge is creating a common core battery. As described above (measurement), the common items within the selected item set need not be identical across studies but must include a minimum number of items that relate to the underlying construct similarly across studies. This provides flexibility for primary data collection. Batteries for individual studies may include a core set of items for a given construct that are then augmented for individual studies to capture differences in the aims of individual investigations or samples of interest. For example, a core set of 8 items may assess antisocial behavior over time in all studies, but a larger set of 10-15 items may be used in three individual studies contributing to this IDA that are tailored to differences in the age ranges of the samples (e.g., ages 2-10, 8-16, and 14-22). This strategy would allow us to create a pooled set of items that include all core items as well as unique items to each study, permitting the collective measure to better capture potential heterotypic continuity (i.e., changes in the indicators of a given construct over time, despite continuity in the construct itself) over development.
