Constraints on cosmological and β parameters for the Euclid-like experiments in the ΛCDM scenario. We assume the scaling relation parameters to be known with a 5% precision and compare the results for the T08 and D16 mass functions, when considering (red and light blue contours) or not (grey and purple contours) the Gaussian prior on the scaling relation scatter β. We show the 68% and 95% c.l. marginalised posterior distributions.