• An Overview of Some Interlaboratory Studies

      Scott, E. Marian; Baxter, M. S.; Aitchison, T. C.; Harkness, D. D.; Cook, G. T. (Department of Geosciences, The University of Arizona, 1990-01-01)
      Many interlaboratory studies have been made in the 14C community at irregular intervals over the past ten years. At times, the results from these studies have been contentious, mostly because of the lack of consistency in their findings. The importance of regular exercises has become particularly acute due to the large number of operating laboratories and the diversity of their methodologies. Hence, we briefly review the studies that have been made in the 1980s, focusing on those in which our laboratories participated. These include the 14C Interlaboratory Comparison in the UK (Otlet et al 1980), the International Comparison (ISG 1982, 1983) and the first two parts of the current International Collaborative Program (Scott et al 1989a, b). The development of each study, its findings and shortcomings, are highlighted in order to assess the concordance of the conclusions.
    • Report on Stage 3 of the International Collaborative Program

      Aitchison, T. C.; Scott, E. Marian; Harkness, D. D.; Baxter, M. S.; Cook, G. T. (Department of Geosciences, The University of Arizona, 1990-01-01)
      This report on the third and final stage of the International Collaborative Program concentrates on the analysis of internal and external variability of 14C dates obtained from samples involved in the full 14C dating process. Thirty-eight laboratories took part in this stage with most producing 8 14C dates from 3 sets of duplicate material (eg, wood, shell and peat) and 2 single samples of wood of known ages 190 yr BP apart. From the 3 sets of duplicates for each laboratory, the internal precision of most laboratories was adequate; 6 labs grossly underestimated their internal reproducibility. From the 14C determinations from the 5 distinct samples for each laboratory, we discovered significant systematic biases, often greater than 100 years, in 15 laboratories and even accounting for bias, 12 laboratories had significantly greater external variability than explained by their quoted errors. In total, 23 out of the 38 laboratories in this stage of the study, FAILED to meet these 3 basic criteria for an adequate performance in the production of 14C dates.