Abstract

If dynamics is measured repeatedly in biological entities like human beings or animals, the diversity of individuals may have a crucial impact on the outcomes of the measurements. An adequate approach for this situation is to assume random coefficients for each individual. This leads to non-linear mixed models, which have attracted an increasing popularity in many fields of applications in recent years due to advanced computer facilities. In such studies main emphasis is laid to the estimation of population (location) parameters for the mean behaviour of the individuals, but besides that also interest may be in the prediction of further response for the specific individuals under investigation. Here we will indicate the problems and implications of this approach to the design of experiments and illustrate various consequences by the simple example of an exponential decay. However, it remains unsolved, what is the “correct” measure of performance of a design in this setting.