ASTM E1950-10

A result must be stated to a sufficient number of digits so that a user receives both quantitative information and a measure of the variability of the value reported.

The range of application of most methods of chemical analysis is based upon the presumption that the quantitative results produced are to be used to compare the analyte content of the test material with specified limiting values. However, analytical results may be used legitimately for other purposes. If the same material is analyzed a number of times or a product is analyzed periodically during an interval of production, each set of results may be averaged to yield an average result having improved reliability, provided nothing has been done between analyses to modify the composition of the analyzed material. Results that fall below the lower limit, although not quantitative individually, contain compositional information and may be reported. The reporting system in this practice permits the analyst to indicate which values are likely to be rendered quantitative by averaging and which are not.

The system is simple enough to be used routinely in reporting results from standard methods and assists those untrained in statistics to apply results appropriately.

1.1 This practice covers the approximate number of digits required to express the expected precision of results reported from standard methods of chemical analysis. This practice provides selection criteria and proper form and symbols for coding results when necessary to indicate the relative reliability of results having small values.

1.2 Specifically excluded is consideration of report forms and the associated informational content of reports in which results are tabulated or transmitted. It is assumed that the reporting laboratory has established a report format to ensure proper identification of the materials tested, the nature and conditions of the test, the responsible personnel, and other related information in accordance with existing regulations and good laboratory practices.