Source parameter distributions for two example parameters. (a) Flux normalisation N₀ of source component A. (b) Power-law index Γ of source component A. The black dashed line and grey band denote the best-fit value and statistical uncertainty of this parameter, also specified in the top right corner. The red line shows the fit of a Gaussian to the histogram, where the fitted mean and width are indicated in the top left corner. The red dashed lines indicate the 1-σ width of the fitted Gaussian, which represents the total (i.e. statistical and systematic) uncertainty on this parameter. The derived systematic error, obtained by subtracting quadratically the statistical error from the fitted total width, is also stated in the figure.