Results of simulations produced by varying the mean value of the input spectral index α₁ (labeled as ). The figure shows the interdependence of the following properties: the input spectral index , the derived spectral index , and the percentage of upper limits below 1 GHz. Left panel: dependence of the input spectral index, , on ; middle panel: dependence of the / ratio on the output spectral index, ; and right panel: dependence of the percentage of upper limits below 1 GHz on . The solid lines show the means derived for different bins in the x-axes of their respective plot, while the colored intervals show the 1σ interval for the same bins. The red point shows the values of spectral index α₁ before and after correction, and the percentage of upper limits below 1 GHz, as presented in Sect. 5. The dashed lines are the equality lines.