Model bias of INCL in terms of equation (30) in the (p,X)n double differential spectra for 800 MeV incident protons and different isotopes as predicted by GP regression. A missing mass number behind the isotope symbol indicates natural composition. The uncertainty band of the prediction and the error bars of the experimental data denote the 2σ confidence interval. Carbon and indium were taken into account in the GP regression but not cadmium and oxygen. The experimental data are colored according to the associated access number (ACCNUM) in the EXFOR database. This shows that all displayed data come from just three experiments [20–22].