Definition Longitudinal study

A longitudinal study is the process of the collection of data, performed recurrently over time on the same statistical unit. Longitudinal data are primarily used to examine time series and to generate forecasts based on those data.

An example of a longitudinal study is the annual measurement of a country's GDP or the daily measurement of the temperature at Mount McKinley.

Surveys will lead to longitudinal data, if the exact same people are interviewed in a panel on the exact same topic repeatedly. The opposite of longitudinal data are cross-sectional data

Please note that the definitions in our statistics encyclopedia are simplified explanations of terms. Our goal is to make the definitions accessible for a broad audience; thus it is possible that some definitions do not adhere entirely to scientific standards.