4.1x00a0;ASTM regulations require precision statements in all test methods in terms of repeatability and reproducibility. This practice may be used in obtaining the needed information as simply as possible. This information may then be used to prepare a precision statement in accordance with Practice E177. Knowledge of the test method precision is useful in commerce and in technical work when comparing test results against standard values (such as specification limits) or between data sources (different laboratories, instruments, etc.).
4.1.1x00a0;When a test method is applied to a large number of portions of a material that are as nearly alike as possible, the test results obtained will not all have the same value. A measure of the degree of agreement among these test results describes the precision of the test method for that material. Numerical measures of the variability between such test results provide inverse measures of the precision of the test method. Greater variability implies smaller (that is, poorer) precision and larger imprecision.
4.1.2x00a0;Precision is reported as a standard deviation, coefficient of variation (relative standard deviation), variance, or a precision limit (a data range indicating no statistically significant difference between test results).
4.1.3x00a0;This practice is designed only to estimate the precision of a test method. However, when accepted reference values are available for the property levels, the test result data obtained according to this practice may be used in estimating the bias of the test method. For a discussion of bias estimation and the relationships between precision, bias, and accuracy, see Practice E177.
4.2x00a0;The procedures presented in this practice consist of three basic steps: planning the interlaboratory study, guiding the testing phase of the study, and analyzing the test result data.
4.2.1x00a0;The planning phase includes forming the ILS task group, the study design, selection and number of participating laboratories, selection of test materials, and writing the ILS protocol. A well-developed test method, including a ruggedness test to determine control of test method conditions, is essential.
Note 1:x00a0;In this practice, the term test method is used both for the actual measurement process and for the written description of the process, while the term protocol is used for the directions given to the laboratories for conducting the ILS.
4.2.2x00a0;The testing phase includes material preparation and distribution, liaison with the participating laboratories, and handling of test result data received from the laboratories.
4.2.3x00a0;The data analysis utilizes tabular, graphical, and statistical diagnostic tools for evaluating the consistency of the data so that unusual values may be detected......
ASTM E691-2016 -
中外标准 -
ASTM-
2016/1 -
现行
关键词：precision repeatability reproducibility repeatability limit reproducibility limit
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