chapter  2
16 Pages

Statistical Assessment of Results of Food Analysis

Most quantitative analytical techniques aim to obtain a measurement such as from chromatography or spectroscopy and relate this to the concentration of a compound in a material such as food. There are two principal needs for statistical methods. The ‘rst is determining how well the concentration of a single sample can be estimated in a laboratory. This may, for example, be a reference sample using a standard method of analysis, and it may be important to compare this against published data or with other laboratories. A second need is during calibration, when establishing a new method, using a series of standards of different concentrations to develop

2.1 Introduction .................................................................................................... 15 2.2 Uncertainty and Precision .............................................................................. 16

2.2.1 Concept ............................................................................................... 16 2.2.2 Origin of Uncertainty ......................................................................... 16 2.2.3 Errors .................................................................................................. 16 2.2.4 Determination of Uncertainty ............................................................ 17 2.2.5 Sampling Uncertainty ......................................................................... 18 2.2.6 Calculation of Uncertainty ................................................................. 18 2.2.7 Con‘dence .......................................................................................... 19 2.2.8 Reporting Uncertainty ........................................................................ 21

2.3 Accuracy and Bias .......................................................................................... 21 2.3.1 De‘nitions........................................................................................... 21 2.3.2 Determination of Accuracy ................................................................ 21 2.3.3 Signi‘cance of Difference in Means ..................................................22