What is a key characteristic of a longitudinal study?

A key characteristic of a longitudinal study is that it observes the same subjects over an extended period. This design allows researchers to track changes and developments in the same individuals, providing insights into dynamics that might be missed in cross-sectional studies, where data is collected at one point in time. By following the same group over time, longitudinal studies can reveal patterns related to development, aging, and the effects of various interventions or life events.

In contrast, other study designs might involve different subjects at each time point or a single moment of data collection, which does not provide the same depth of understanding about change. Additionally, while longitudinal studies may sometimes use theoretical frameworks, they primarily emphasize empirical observation of actual subjects across a timeline rather than just focusing on abstract concepts.