The systematic determination of accuracy and precision in geochemical exploration data

Regional geochemical data from the 1:250,000 map series of Great Britain produced by the Institute of Geological Sciences are processed using a computer system developed for the National Geochemical Data Bank. The system, which can be used for the selective or complete retrieval of data and for statistical analysis and plotting, incorporates a procedure for determining accuracy and precision. Changes in accuracy are monitored by analysis of standards and the redetermination of sub-sets of samples using an instrumental neutron activation method. Samples are assigned random numbers in the field and are re-ordered sequentially prior to preparation and analysis in order to determine systematic errors occurring within batches of samples.Sampling, sub-sampling and analytical precision are monitored using analysis of variance methods on the results obtained on duplicate samples and analyses. The system for the efficient processing of this information is described and examples of the different types of error presented.