Comparison of the predicted pseudo-power spectra (dotted red curves) with the mean power spectra measured from 25 simple simulations (points with error bars; see text of Section 5 for details). The upper panel shows |$\widetilde {C}_\ell ^{EE}$| and the lower panel shows |$\widetilde {C}_\ell ^{BB}$|⁠. The predicted B mode pseudo-power spectrum in the case of zero input E modes is also shown in the lower panel as the dotted blue curve.