Meeting the ISO/IEC Requirements for Traceability and Measurement Uncertainty APLAC Approaches Dr Bernard King NARL, Australia

Interpretation of ISO/IEC Requirements P Extensive consultation leading to common interpretation and new Guides P APLAC held 3 day Workshop in May 01 to develop a common interpretation, across five fields. P Draft guide produced P Final guide expected by end of 2002 P Will supplement an ILAC guide

Some of the Difficulties P Anxiety in labs and accreditation bodies P Need for training of lab staff and assessors P Time / cost of additional work P Lack of customer demand P Some countries / fields are moving faster than others Need to interpret requirements in a pragmatic, progressive and common sense way ILAC MRA will help ensure level playing field

Interrelated Requirements in ISO/IEC é Specification of measurement requirement é Method validation é Traceability é Measurement Uncertainty

ISO/IEC Method Validation Requirements é Specifically required for in-house methods é Implicitely required for all methods é Long standing requirement, but often inadequately addressed é Needs to be subject to closer scrutiny If method validation data is available, then evaluating MU is not difficult

ISO/IEC Traceability Requirements P Measurements must be traceable to SI, where feasible P Where above is not feasible, traceability to other measurement standards must be established P This can be achieved by use of transfer standards, that are themselves traceable to higher level standards

Example 1- Cd in soil P Measurand &Units - Total Cd in soil, measured in mg/kg P Equation C = I. dC. V mg/kg dI m. R P I. dC is traceable to SI through PSRM dI P R is traceable to SI through matrix RM or... P m and V are traceable to SI through calibrated standards If the model is valid then C is also traceable to SI

Traceability of RMs

ISO/IEC MU Requirements 3 An uncertainty evaluation is required for all measurements 3 Labs shall at least attempt to: é identify all significant components é make a reasonable estimation of U é ensure that reported results do not give a false impression of U.

Reproducibility Based MU Combine other significant effects with reproducibility Reproducibility MU Bias Effects Sampling Effects

Summary of International MU Policy P Target implementation date - Dec 2002 P ISO GUM and Eurachem / CITAC strategies are recommended but not compulsory P Strategies based on reproducibility need to also consider other significant effects P MU estimates can be based on available or readily obtainable data, including professional judgement P The degree of rigour required in evaluating uncertainty depends on the end use of the measurement

cont... PThe evaluation of uncertainties associated with qualitative tests is not required, but the probability of false identification does need to be considered. PAny limitations associated with traceability and MU claims need to be reported with results PIt is expected that reporting MU, where relevant and necessary, will become the norm with time

Conclusions P Measurements need to facilitate sound decisions P Effort required depends on the level of acceptable MU PA matter for professional judgment P Not as difficult as it first seems P Eg- If validation data available MU takes 0.5 to 2 days PReasonable progress is being made in implementing the new requirements in a pragmatic and harmonized way.

Sources of Help P Literature - policy papers, guides, journals, web P Training courses, seminars, workshops, P eg. On RMs, MU and validation P Web- based training on MU at