1 - Process for determining similarities of signals from a sample analysis step using the same type of measuring device, characterized in that it comprises: a step of determining a value for each parameter of an uncertainty model related to said signals by processing homologous characteristic elements in at least two signals derived from the analysis of similar samples, and a step of determining a similarity measurement between signals based on each parameter value of the said uncertainty model and of homologous characteristic elements in the signals whose similarity is being measured.