Longitudinal Studies

Longitudinal studies or panel studies are studies where the research settings involve multiple follow-up measurements on a random sample of individuals, such as their achievement, performance, behavior, or attitude, over a period of time with logically spaced time points. The purpose of longitudinal research studies is to gather and analyze quantitative data, qualitative data, or both, on growth, change, and development over time. Generally, the significance of the longitudinal research studies stems from the fact that the knowledge, skills, attitudes, perceptions, and behaviors of individual subjects usually develop, grow, and change in essential ways over a period of time. Longitudinal studies require formulating longitudinal research questions and hypotheses, using longitudinal data collection methods (e.g. panel surveys), and using longitudinal data analysis methods.

Researchers across disciplines have used different terms to describe the design of the longitudinal studies that involve repeatedly observing and measuring the same individual subjects (respondents) over time. Some of the terms used are longitudinal research designs, repeated-measures designs, within-subjects designs, growth modeling, multi-level growth modeling, time-series models, and individual change models.