Panel a) histogram for the number of pixels as a function of the signal-to-noise ratio in the polarization profiles. Circular polarization (Stokes V) is indicated by the solid line, while the linear polarization () is shown dashed. Panel b) histogram for the magnetic field strength . Panel c) histogram for the inclination of the magnetic field vector γ. Panel d) histogram for the magnetic filling factor α_mag. In the last three panels, the dashed lines display the histograms obtained from those pixels where any of three polarization profiles has an SNR ≥ 3, whereas solid and dashed lines represent SNR ≥ 4.5,6, respectively. These thresholds are also indicated with vertical lines in panel a. This figure corresponds to map A, where the characteristic noise level is σ_s = 10^-3.