ISO 8466-2:1993

Water quality — Calibration and evaluation of analytical methods and estimation of performance characteristics — Part 2: Calibration strategy for non-linear second order calibration functions

Is intended for use in method development and may not necessarily be applicable to all routine analyses. It is not always possible to accurately describe the relationship between a set of calibration points with a rectilinear curve, even by decreasing the working range. Instead of the linear regression analysis, a least squares fit to a second order polynomial is applied. Using this, it is possible to calculate not only the calibration function but also the confidence interval associated with it.