IS/ISO 11843 : PART 2 : 2000 : Capability of Detection Part 2 Methodology in the Linear Calibration Case

NATIONAL FOREWORD

This Indian Standard (Part 2) which is identical with ISO 11843-2 : 2000 ‘Capability of detection — Part 2: Methodology in the linear calibration case’ issued by the International Organization for Standarization (ISO) was adopted by the Bureau of Indian Standards on the recommendation of the Statistical Methods for Quality and Reliability Sectional Committee and approval of the Management and Systems Division Council.

An ideal requirement for the capability of detection with respect to a selected state variable would be that the actual state of every observed system can be classified with certainty as either equal to or different from its basic state. However, due to systematic and random distortions, this ideal requirement cannot be satisfied because:

— in reality all reference states, including the basic state, are never known in terms of the state variable. Hence, all states can only be correctly characterized in terms of differences from basic state, that is, in terms of the net state variable.

— in practice, reference states are very often assumed to be known with respect to the state variable.

In other words, the value of the state variable for the basic state is set to zero; for instance in analytical chemistry, the unknown concentration or the amount of analyte in the blank material usually is assumed to be zero and values of the net concentration or amount are reported in terms of supposed concentrations or amounts. In chemical trace analysis especially, it is only possible to estimate concentration or amount differences with respect to available blank material. In order to prevent erroneous decisions, it is generally recommended to report differences from the basic state only, that is, data in terms of the net state variable.

— the calibrations and the processes of sampling and sample preparation add random variation to the measurement results.