A description is provided of the analytical and statistical methods used in a study of the later prehistoric pottery of the Western Isles of Scotland. The accuracy and precision of the methods used are discussed and results are presented for the analysis of a set of clay samples from known locations. The study indicates that the methods employed provide an adequate means of characterizing clays from the various sources used. In addition the use of ratios of element concentrations to the scandium concentration for individual samples provides a better classification than does the use of concentrations rather than ratios.