Training sample for the RF algorithm. The contours represent the distribution of the 869 high-confidence associations, while the orange dots represent the fake associations. The spectral parameters for the training sample are shown in terms of the γ-ray photon index, Γ; the three MIR colors, c₁₂, c₂₃, and c₃₄ (as defined in the last paragraph of Section 1); and the MIR radio-loudness, q₂₂.