Left panels: the cumulative probabilities (P, black lines) and the confidence levels (σ, red lines) as functions of ﹩{\rho }_{{\rm{s}}}﹩ derived from the currently identified FSRQs (dashed lines) and BL Lacs (solid lines) observed with Fermi/LAT. Cross points “A” indicate a confidence level of 50% for classifying the two types of blazars. The shaded regions defined with cross points “B” and “C” indicate the percentages of sources and ﹩{\rho }_{{\rm{s}}}﹩ at a confidence level of 90%. Right panels: distributions of BCUs together with the ﹩{\rho }_{{\rm{s}}}﹩ contours derived from our reference samples in the corresponding planes. The red pentagons, green stars, and blue circles indicate BCU-Is, BCU-IIs, and BCU-IIIs, respectively.