[Roaming through methodology. XXII. Application of techniques for longitudinal data analysis].

Longitudinal studies are characterised by repeated measurements of the outcome variable on the same individuals. This implicates that observations are correlated and that statistical techniques, such as linear regression analysis cannot be used. Special longitudinal techniques correct for the dependency in repeated observations by analysing the development of a certain individual in time. Depending on the research question, the distribution of the outcome variable, and the number of repeated measurements, a certain technique should be chosen. Sophisticated longitudinal techniques like generalized estimating equations and random-coefficient models are most recommendable.