|New Proficiency Testing Standard to Aid in Interlaboratory Studies
ASTM International Committee E11 on Quality and Statistics has approved a new practice that describes methods for proficiency testing providers to use in analyzing laboratory results obtained in their programs. The standard, E 2489, Practice for Statistical Analysis of One-Sample and Two-Sample Interlaboratory Proficiency Testing Programs, is under the jurisdiction of Subcommittee E11.20 on Test Method Evaluation and Quality Control.
Many proficiency testing programs request that participating laboratories perform testing in accordance with ASTM test methods and the amount of information gathered from testing can be substantial. Over the course of several rounds of testing, the relevant ASTM test methods are sometimes revised. The proficiency testing results should reflect improvements due to those revisions to the test methods, so results from proficiency testing can provide feedback to ASTM subcommittees. Furthermore, the number of participants in proficiency testing programs can be substantially larger than might have been available when the precision statement for a test method was developed. In addition, many proficiency testing providers have developed their own methods of analysis because applicable ASTM standards did not exist.
For these reasons, it was felt that there was a need for Committee E11 to develop a practice describing methods that proficiency testing providers can use to analyze laboratory results obtained in their programs. Ron Holsinger, supervisor, proficiency sample program, AASHTO Materials Reference Laboratory, says that proficiency testing providers and ASTM subcommittees charged with maintaining, developing and improving test methods will find Practice E 2489 useful.
“The practice describes robust methods for the statistical analysis of laboratory results for proficiency testing programs based on one-sample or two-sample schemes,” says Holsinger. “The methods of analysis are applicable to small (a minimum of 10 laboratories) and large datasets. The approach presented minimizes the effect of extreme values in a dataset and effectively eliminates the need to identify outliers.”
Holsinger also notes that the practice provides a means to establish ranges of results that can be used to assess individual laboratory performance and to estimate the precision of a test method, applicable to the property levels and material types included in the program.
Subcommittee E11.20 is seeking individuals who are interested in developing complementary companion standards for other types of proficiency testing programs and in promoting the use of feedback from proficiency testing programs by ASTM subcommittees and other standards developers.
Technical Information: Ron Holsinger, AASHTO Materials Reference Laboratory, NIST, Gaithersburg, Md. Phone: 301/975-6277
ASTM Staff: Christine Sierk
ASTM International Headquarters
West Conshohocken, Pa.