Controlling the uncertainties and the documentary lacks of an archaeological corpus should be the priority to interpret correctly the data distribution. The conception of a reliability map in order to estimate the quality of the inventory, the creation of a representation map so as to highlight the over- and under-representations and finally their combination, the confidence map, are efficient tools to spot out the zones concerning which there is a risk for a defective interpretation. We propose here, an application on a case-study of Middle Bronze Age metal hoards and isolated finds, for which the only really determining factor is the possibility for discoveries since they came almost exclusively from chance finds. It can be evaluated after the contemporary population density, and the modern works implying the digging up the soil.