Left panel: faint spectral index α₂ vs. the bright spectral index α₁ for the 0.5–2 keV band and for the 2–10 keV band in the left top and left bottom panel, respectively, and faint spectral index α₂ vs. the flux break S₀ for the 0.5–2 keV band and for the 2–10 keV band in the right top and right bottom panel, respectively (see text for the definition of α₁, α₂ and S₀). The red solid squares are our results for broken power law model, and the black open dots represents a compilation of data from literature: Hasinger et al. (1993), Giommi et al. (2000), Mushotzky et al. (2000), Page et al. (2000), Brandt et al. (2001), Baldi et al. (2002), Cowie et al. (2002), Rosati et al. (2002), Harrison et al. (2003), Moretti et al. (2003), Bauer et al. (2004), Kim et al. (2004), Yang et al. (2004), Hasinger et al. (2005), Kenter et al. (2005), Cappelluti et al. (2007), Brunner et al. (2008), Carrera et al. (2007), Mateos et al. (2008), Ueda et al. (2008), Cappelluti et al. (2009). Right panel: ratio between the binned integral log N–log S and the best fit model in the 0.5–2 keV band (upper panel) and 2–10 keV band (bottom panel). The dotted lines are the ratio between the binned integral log N–log S and predicted 1-σ uncertainty interval.