Top three panels: residuals in D_ℓ between the fit results and the theoretical CMB power spectrum. The dark grey line shows the theoretical CMB spectrum downscaled by a factor of 0.2 for readability. Bottom panel: mismatch between the model and the data after the fit as defined by Eq. (3.1) and the thin dashed line shows the expected mismatch per bin. Only one point every three bins is displayed. Left panel: filled dots show differences between CMB spectra obtained from fit on simulations with respect to input CMB spectrum at each bin, at f_sky = 0.5, shown in dark red for SET1, yellow for SET2, and black for SET3. Right panel: filled dots show differences between CMB spectra obtained from the fit on Planck 2015 half-mission data and the Planck best fit ΛCDM Plik spectrum.