2. General strategy for building a robust calibration

When the robustness of a calibration is of particular interest, and a quantity G (assumed to be unique for simplicity's sake) is involved, the construction of the model must follow a hierarchical approach, as shown in figure 5 . This flowchart uses 3 levels of questioning.

• First, we need to decide how much influence G has on the calibration. This first step is made tricky by the multivariate aspect of the measured signals. In the monovariate case, an influence of G on the signal necessarily implies an influence on