ABSTRACT
Depending on how often research studies collect data, they are classified as either cross-sectional or longitudinal. When data is collected from participants at one point in time, it is cross-sectional research. When researchers return over time with the same question to a population or even the same sample, it is longitudinal research. Even if it takes researchers months to collect all the surveys or complete the experiment, it is still considered cross-sectional because each data point was gathered from each individual or experiment at one discrete moment in time. In longitudinal research, the individual participants may be the same but need not be; what matters is that the population being sampled is the same, as are the questions. Data for longitudinal studies are usually not collected continuously. At specified times, cross-sectional data is collected. Panel studies are a form of longitudinal research that collects the same measures from the same people at different points in time.
