Histogram of the uncertainties of the determined spectral indices. The black line includes all sources for which we are able to determine a spectral index; the gray shaded area represents the sources for which we have an intensity measurement in all 6 SPWs, and therefore the spectral index α is derived from fitting all 6 SPWs; the red line includes sources fitted with 5 SPWs; the blue line includes sources fitted with 4 SPWs; the green line includes sources fitted with 3 SPWs; and the purple line includes sources fitted with 2 SPWs.