Estimation of the goodness of fit of the fiducial best-fit model at the MAP values. The histogram shows the distribution of the χ² values from 200 noisy mock data vectors (see the main text for the detailed procedure). The orange line shows the fit of the χ² distribution to the histogram, from which we obtain the effective number of degrees of freedom in the data. The vertical black line shows the χ² value as obtained from the best-fit model to the real data.