Abstract
The basic requirement for a good calibration is representative data. This paper outlines techniques for selecting samples from an existing population. The concept of factorial designs is explained, and three ways of applying experimental design to generate representative data are described. These are: to vary the experimental conditions; focus on some of the parameters of interest directly (reference values); to vary the underlying conditions which generate consistent variations in the spectra,for example production factors. Finally the paper gives an example of the use of the concept of experimental design to pick out samples from a population.