Percentile points 90%, 95%, and 99% for the distribution of C for simulated Perseus (top) and Capella (bottom) spectra. The expected value C_e was subtracted and the difference is scaled with . The percentile points are shown as a function of the average number of counts in the spectra. The dotted lines show the expected percentile values if the distribution of C had been normal. These values are reached asymptotically for large numbers of counts in the spectra.