1. Data

1.1 Longitudinal data

Longitudinal data are data measured repeatedly in the same subject, inducing correlation between observations. In pharmacometrics, these data are obtained during clinical drug trials. They are collected from all subjects several times over time, during different treatment periods (occasions); their number may differ from one subject and/or occasion to another. The data collected has a hierarchical structure: observations can be grouped together as belonging to the same entity, the subject or individual. Each subject is different, with specific PK and/or PD parameters and therefore different from those of the population, i.e. the "average" subject. For each subject, demographic, genetic, physiological and environmental factors are collected. Called covariates,...