root-mean-square (RMS) is calculated from the differences between the certified values of the standards, and the values as calculated from the calibration curve. The K value is calculated in essentially the same way as the RMS, but each residual value is weighted by the square root of the concentration. This value is less sensitive to the actual concentration range. The correlation and relative errors for each curve are also presented. The slope of the calibration curve is calculated in units of concentration over intensity. The Ratio Channel identifies which secondary target Compton line is used to correct for differing matrix effects.