1.1 This practice describes the techniques for planning, conducting, analyzing, and treating the results of an interlaboratory study (ILS) of a test method. The statistical techniques described in this practice provide adequate information for formulating the precision statement of a test method.
1.2 This practice does not concern itself with the development of test methods but rather with gathering the information needed for a test method precision statement after the development stage has been successfully completed. The data obtained in the interlaboratory study may indicate, however, that further effort is needed to improve the test method.
1.3 Since the primary purpose of this practice is the development of the information needed for a precision statement, the experimental design in this practice may not be optimum for evaluating materials, apparatus, or individual laboratories.
1.4 Field of Application—This practice is concerned exclusively with test methods which yield a single numerical figure as the test result, although the single figure may be the outcome of a calculation from a set of measurements.
1.4.1 This practice does not cover methods in which the measurement is a categorization; however, for many practical purposes categorical outcomes can be scored, such as zero-one scoring for binary measurements or as integers, ranks for example, for well-ordered categories and then the test result can be defined as an average, or other summary statistic, of several individual scores.
1.5 The information in this practice is arranged as follows:
| Section |
Scope | 1 |
Referenced Documents | 2 |
Terminology | 3 |
Summary of Practice | 4 |
Significance and Use | 5 |
| |
Planning the Interlaboratory Study (ILS) | Section |
ILS Membership | 6 |
Basic Design | 7 |
Test Method | 8 |
Laboratories | 9 |
Materials | 10 |
Number of Test Results per Material | 11 |
Protocol | 12 |
| |
Conducting the Testing Phase of the ILS | Section |
Pilot Run | 13 |
Full Scale Run | 14 |
| |
Calculation and Display of Statistics | Section |
Calculation of the Statistics | 15 |
Tabular and Graphical Display of Statistics | 16 |
| |
Data Consistency | Section |
Flagging Inconsistent Results | 17 |
Investigation | 18 |
Task Group Actions | 19 |
Glucose ILS Consistency | 20 |
| |
Precision Statement Information | Section |
Repeatability and Reproducibility | 21 |
| |
Appendixes | Appendix |
Theoretical Considerations | X1 |
Pentosans in Pulp Example | X2 |
| |
References | |
| |
Tables and Figures | |
| Table |
Glucose in Serum Example | 1–4, 6–8 |
Critical Values of Consistency Statistics, h and k | 5 |
| |
| Figure |
Glucose in Serum Example | 1–3 |
1.6 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.