What is a longitudinal study?

A longitudinal study is characterized by its design that involves repeated observations of the same variables over an extended period. This approach allows researchers to track changes and developments over time within the same subjects, which can provide insights into trends, long-term outcomes, and causal relationships. By collecting data across multiple time points, the study can reveal how specific factors influence the subjects as they age or as circumstances change, making it a powerful tool in various fields including psychology, sociology, and medicine.

In contrast, the other choices describe methodologies that do not fit the definition of a longitudinal study. Some suggest one-time observations or a focus solely on past data, neither of which involve the ongoing data collection characteristic of longitudinal studies. A method that samples different groups emphasizes cross-sectional studies rather than the repeated measures over time that define longitudinal research. Understanding this distinction is crucial for recognizing the strengths and applications of longitudinal studies in research.