Which study exemplifies a longitudinal research design?

A longitudinal research design is characterized by collecting data from the same subjects repeatedly over a period of time, allowing researchers to observe changes and developments in those subjects. The 7UP study is a prime example of this approach, as it follows the same group of individuals from childhood into adulthood, gathering insights about their lives and social circumstances at various stages.

In contrast, the other studies mentioned involve different methodologies. Curtis's study of Genie focuses on a case study of a specific individual, which does not represent longitudinal tracking due to its limited scope and timeframe. King's investigation of school dynamics likely involves a snapshot of a specific period within a school setting, rather than ongoing data collection. Patrick's gang study in Glasgow, although it may have involved observations over time, does not have the same extended duration or repeated engagement with the same individuals as seen in the 7UP study. Thus, the 7UP study stands out as the best example of longitudinal research design.