Testing the (P, φ₃₁) → FEH fit residuals. Inset: Ordered distribution (light blue) of the residuals (ΔFEH = |FEH_obs – FEH_fit|) for set A of Table 3. Black line shows the distribution of the corresponding Gaussian, fitting the core of the observed residuals. Main panel: Difference between the observed and the predicted Gaussian residuals. The 3σ ranges for the Gaussian residuals are shown by the vertical error bars.