Distribution of the difference between cosmological parameter mean posterior values, as estimated by Plik (assuming foreground spectra are known) from the (CMB + fixed foregrounds + noise) FFP6 simulations, and the corresponding posterior parameter mean values from CMB only simulations (based on the same CMB realisations as in the FFP6 simulations), in units of the FFP6 posterior standard deviations.This demonstrates the absence of methodological bias at the level of the intrinsic dispersion between realisations, while removing from the distributions the dominating scatter coming from the purely CMB induced cosmic variance. In these figures, the dominant source of scatter comes from the CMB-foreground chance correlations in the signal dominated part of the spectrum, and from the noise scatter at large multipoles.