Concentration–mass relation for the CHEX-MATE sample. The error bars indicate 68% uncertainties in the parameters; we highlight in light blue the clusters with $\mathrm{Log}(M_{200}^M/M_{\sigma ,200c})>0.3$. The dashed blue line is the best-fit Bayesian linear regression derived using the Sereno & Ettori (2015b) method; the shaded region represents the corresponding 1σ contour. Purple and red crosses indicate the values obtained by stacking clusters in bin of SZ mass and σ_ap, 200, as explained in Sect. 5. The solid brown line shows the theoretical prediction of Diemer & Joyce (2019).