develop consensus standards for use by TNI's programs. This group has a support role in assisting other programs with activities such as guidance and standards interpretation.
fosters the generation of data of known and documented quality is through the National Environmental Laboratory Accreditation Program, or NELAP. The purpose of this program is to establish and implement a program for the accreditation of environmental laboratories.
is to establish and maintain a national PT program to support TNI’s National Environmental Laboratory Accreditation Program, and other activities.
Field Activities Program (NEFAP) Executive Committee is to establish and implement an accreditation program for field sampling and measurement organizations (FSMOs).
Audit Sample Program is to develop consensus standards for the manufacture and analysis of audit samples for source emission testing.
on a variety of topics of interest to the environmental measurement community. TNI also hosts two regularly scheduled meetings per year, typically in January and August. Both are a week long and involve open meetings of TNI committees as well as training courses and other special sessions.Standard Interpretation
Standard: 2003 NELAC
Section: 5.5.4.6.1
Link to relevant standard
REQUEST:
Please explain what types of procedures for estimating uncertanity of measurements. I am not sure which area you mean. Thank You
TNI FINAL RESPONSE:
(Quality System Expert Committee/NELAP Accreditation Council, x-x-10)
The following is a previously issued statement regarding uncertainty (found on the TNI Website - Previous Interpretations): Uncertainty Clarification - Section 5.5.4.6 "Estimation of Uncertainty of Measurement" has created some confusion. Please note that as a laboratory it is impossible for you to calculate "Total Uncertainty" unless you are given all of the additional pieces from external sources to the lab itself. This section is intended to advise a laboratory to have a "Procedure on Uncertainty for the Laboratory Portion" in place, so that if requested by a client it could be determined. The key language within this section can be found in Section 5.5.4.6.2, " ... In certain cases the nature of the test method may preclude rigorous, metrologically and statistically valid, calculation of uncertainty of measurement. In these cases the laboratory shall at least attempt to identify all the components of uncertainty and make a reasonable estimation, and shall ensure that the form of reporting of the result does not give a wrong impression of the uncertainty. ..."
The laboratory can arrive at an estimation of uncertainty through a review of quality control data. For example, a comparison of CCV data and LCS data could lead to an estimate of the uncertainty caused by the preparation process. A similar comparison between LCS data and MS data could lead to an estimate of the uncertainty introduced by the sample matrix. Organizations (such as A2LA and the Department of the Navy) have developed tools to aid a laboratory in accomplishing this task.