Dependence of our goodness-of-fit parameter, X, depends on the free parameters a and b. Upper panel: X against a considering only the 1 M_⊙ mass bin. The vertical dashed line shows our best fit value of a ≈ 1.33. Middle panel: X against b assuming the above best fit value for a and taking into account all three mass bins. The vertical dashed line shows our best fit value of b ≈ −3.36. Lower panel: a contour plot of X against both a and b, taking into account all mass bins. The red cross shows the location of a = 1.33 and b = −3.36, and the blue cross shows the location of a = 1.40 and b = −3.17, corresponding to the minimum of X for all values of a and b.