Agreement analysis in the arena of complex variability

Agreement studies examine how closely different medical devices, methods or raters measure the same quantity, and are very common in medical research. However, in the arena of complex variability, standard methods cannot be used and more sophisticated approaches are necessary. In this case study, the author illustrates the process and challenges of conducting an agreement analysis in this context. Mixed modelling is the foundation for conducting a successful agreement analysis in the presence of complex variability.