Answer: Longitudinal data is desirable when researchers want to study changes in variables over time. This type of data collection is useful when investigating long-term trends, patterns, or effects of certain factors on a specific group or population.
Therefore, longitudinal data would be desirable in situations where the researcher is interested in studying the changes that occur within a group of people over time, rather than just taking a snapshot of their behavior or attitudes at a particular moment.
For example, if a researcher wants to study the effects of a particular treatment or intervention on a group of patients, it would be desirable to collect longitudinal data to assess the impact of the treatment over time. Similarly, if a researcher wants to study the long-term effects of an educational program on students' academic performance, longitudinal data would be necessary to track the progress of students over a period of time.
In general, longitudinal data is desirable when studying any phenomenon that occurs over time, whether it is physical, behavioral, or social. It is important to note, however, that collecting longitudinal data can be time-consuming, expensive, and require significant effort to maintain participant engagement.
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