Likelihood contours in the slope-intercept-scatter planes, for a linear fit to the full α.btfr sample including intrinsic scatter as a free parameter. Left panel: the black cross denotes the best fit values of slope, α, and intrinsic scatter, σ_{⊥ ,intr}. The solid lines represent the 1σ, 2σ, and 3σ error regions in the α–σ_{⊥ ,intr} plane. Right panel: the black cross and black contours represent the best fit value and error regions for the slope, α, and intercept, β. The gray cross and contours represent the results of our fiducial no-scatter fit to the full α.btfr sample (same as Fig. B.1).