14. Precision and Bias
14.1 The precision of this test method was determined by statistical examination of interlaboratory study results. All data was generated using GC/ECD.
14.1.1 Repeatability - The difference between two results obtained by the same operator with the same apparatus under constant operating conditions on identical test materials would, in the long run, in the normal and correct operation of the test method exceed the following values only one case in twenty:
where X is the average PCB concentration in mg/kg.
14.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical materials would in the long run, exceed the following values only in one case in twenty.
where X is the average PCB concentration in mg/kg.
14.1.3 Precision estimates for selected values of X are set out in the following Table 1:
14.2 Bias - A reliable quantitation of bias was not possible due to the manner in which the samples were prepared and aliquoted. However, the method tends to produce a result that is low. This tendency is mitigated to some extent through the use of a surrogate as described in Section 11.
15. Keywords
15.1 gas chromatography; GC/ECD; PCBs; polychlorinated biphenyls