Maximum amplitude of the LSD Stokes V profiles as a function of the absolute value of the mean longitudinal magnetic field. The observations for which a polarisation signal is definitely detected and  ⟨ B_z ⟩  is measured at  >3-σ significance are shown with squares. Circles correspond to the observations for which  ⟨ B_z ⟩  is not significant, but polarisation signal is still detected. The triangle in the lower-left corner corresponds to a single non-detection of the polarisation signal in the LSD Stokes V profile.