1 aiha-lap, llc webinar measurement uncertainty and traceability policies review friday, april 30,...

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AIHA-LAP, LLC Webinar

Measurement Uncertainty and

Traceability Policies Review

Friday, April 30, 2010

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Webinar Outline

• Introduction of Presenters/Moderators • Ground Rules• Background • What’s New• Basis of the new Policies• Policy Review - Section by Section • Discussion of guidance and examples• What to Expect Beginning April 1• Questions and Answers

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Webinar Speakers

• Speakers:– Margie Breida – Ronald Peters (MU)– Maureen Hamilton (Traceability)

• Moderator: – Sage Morgante

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Ground Rules

• All phone lines will be muted during the presentation.

• Speakers will present information in the slides. • Questions can be be typed in the chat box

during the presentation. Participants should type in their name/laboratory and a question.

• When the speaker thinks it is appropriate to take questions, he/she will pause and the moderator will read the questions.

• We will answer as many questions as we can, but not all questions will be answered.

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Ground Rules (cont’d)

• If you experience technical problems or you cannot connect to the call, please contact us at (703) 846-0739.

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Background• AIHA-LAP, LLC evaluation for

international recognition (APLAC/IAAC)– MU and traceability changes needed so that

we are more aligned with other accreditation bodies

• New policies, guidance and examples replace previous guidance.

• New MU and traceability documents posted on web site on February 18, 2010.

• Became effective April 1, 2010.• All assessments are now being

conducted against these new policies.

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What’s New?

• Follow links to the 2010 AIHA-LAP, LLC Policy Modules

• Appendix G– Policy on the Estimation of Uncertainty

of Measurement (Rev. 0, effect. April 1, 2010)

• Guidance on the Estimation of Uncertainty of Measurement (Rev. 1, 2/17/10)

• Guidance on Statistical Analysis of EMLAP QC (Rev. 1, 2/17/10)

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What’s New?

• Appendix H

– Policy on Traceability of Measurement (Rev. 0, effect. April 1, 2010)

• Guidance on Traceability of Measurement (Rev. 1, 2/17/10)

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What’s New?

• Example Excel Workbooks:

– CALA Example Internal Calibration Workbook– Example Chemistry Measurement Uncertainty

Calculations– Example Microbiology Measurement Uncertai

nty Calculations

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Important to Remember!

• Policy Documents – Include Requirements

• Guidance Documents – Include guidance and recommendations – These are NOT Requirements but include acceptable approaches

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Policy on the Estimation of Uncertainty of Measurement

(MU Policy)• 1. Scope • 2. References• 3. Terms and Definitions• 4. Background• 5. AIHA-LAP, LLC Uncertainty Policy• 6. Assessment for Accreditation• 7. Guidance and Examples

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Basis of MU Policy/GuidanceReferences

• ISO/IEC 17025:2005 - General Requirements for the Competence of Testing and Calibration Laboratories

• Guide to the Uncertainty of Measurement (GUM) published by ISO, IEC, CIPM, BIPM, Eurachem, etc

• Quantifying Uncertainty in Analytical Measurement, 2nd Edition, 2000, Eurachem/CITAC

• APLAC TC 005 (2006) Interpretation and Guidance on the Estimation of Uncertainty of Measurement in Testing, Asia-Pacific Laboratory Cooperation

• ILAC Guide 17: Introducing the Concept of Uncertainty of Measurement in Testing in Association with the Application of the Standard ISO/IEC 17025. 2002, ILAC: Rhodes, NSW, Australia.

• CALA P19 – CALA Policy on the Estimation of Uncertainty of Measurement in Environmental Testing.

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Basis of MU Policy

REQUIREMENTS

• ISO/IEC 17025 Section 5.4.6.2 “Testing laboratories shall have and shall apply procedures for estimating uncertainty of measurement.”

• ISO/IEC 17025 Section 5.4.6.3 “When estimating the uncertainty of measurement, all uncertainty components which are of importance in the given situation shall be taken into account using appropriate methods of analysis.”

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Basis of MU Policy/Guidance

Key Terms and Definitions

• uncertainty of measurement (VIM 2.26 JCGM 200:2008): non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used

• NOTE 1 Measurement uncertainty includes components arising from systematic effects, such as components associated with corrections and the assigned quantity values of measurement standards, as well as the definitional uncertainty. Sometimes estimated systematic effects are not corrected for but, instead, associated measurement uncertainty components are incorporated.

• NOTE 2 The parameter may be, for example, a standard deviation called standard measurement uncertainty (or a specified multiple of it), or the half-width of an interval having a stated coverage probability.

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• uncertainty of measurement (VIM 2.26 JCGM 200:2008):

• NOTE 3 Measurement uncertainty comprises, in general, many components. Some of these may be evaluated by Type A evaluation of measurement uncertainty from the statistical distribution of the quantity values from series of measurements and can be characterized by standard deviations. The other components, which may be evaluated by Type B evaluation of measurement uncertainty, can also be characterized by standard deviations, evaluated from probability density functions based on experience or other information.

• NOTE 4 In general, for a given set of information, it is understood that the measurement uncertainty is associated with a stated quantity value attributed to the measurand. A modification of this value results in a modification of the associated uncertainty.

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Basis of MU Policy

REQUIREMENTS

• ISO/IEC 17025 Section 5.10.3.1 “In addition to the requirements listed in 5.10.2, test reports shall, where necessary for the interpretation of the test results, include the following:

c) where applicable, a statement on the estimated uncertainty of measurement; information on uncertainty is needed in test reports when it is relevant to the validity or application of the test results, when a customer's instruction so requires, or when the uncertainty affects compliance to a specification limit;”

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5.0 AIHA-LAP, LLC Uncertainty Policy

• The requirement which underlies this policy is given in ISO/IEC 17025, Clauses 5.4.6 and 5.10.3.1 c).

• Laboratories accredited under the AIHA-LAP, LLC Accreditation Program shall fulfil the following requirements with respect to the estimation of uncertainty of measurement for tests associated with their scope of accreditation:

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AIHA-LAP, LLC Uncertainty Policy

• 5.1 Laboratories shall be able to demonstrate their ability to estimate measurement uncertainty for all accredited quantitative test methods. In those cases where a rigorous estimation is not possible, the laboratory must make a reasonable attempt to estimate the uncertainty of test results. All approaches that provide a reasonable and valid estimation of uncertainty are equally acceptable.

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• 5.2 Laboratories shall make independent estimations of uncertainty for tests performed on samples with significantly different matrices. For example, estimations made for filter samples cannot be applied to bulk samples.

• 5.3 Estimations of measurement uncertainty are not needed where the reported test results are qualitative. Laboratories are, however, expected to have an understanding of the contributors to variability of test results. Examples of such tests are those that report only organism identifications or presence/absence.

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• 5.4 Laboratories shall have a written procedure describing the process used to estimate measurement uncertainty, including at a minimum:

– 5.4.1 Definition of the measurand.

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Basis of MU Policy/GuidanceKey Terms and Definitions

• measurand (VIM 2.3 JCGM 200:2008): quantity intended to be measured

• NOTE The specification of a measurand requires knowledge of the kind of quantity, description of the state of the phenomenon, body, or substance carrying the quantity, including any relevant component, and the chemical entities involved.

• NOTE In chemistry, “analyte”, or the name of a substance or compound, are terms sometimes used for ‘measurand’. This usage is erroneous because these terms do not refer to quantities

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– 5.4.1 Definition of the measurand.– 5.4.2 Identification of the contributors to

uncertainly.

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MU Guidance Document

Consider the following categories or processes as listed by CALA and ILAC Guide 17:

• Sampling or sub-sampling – in-house sub-sampling typically applies only to bulk samples tested in AIHA-LAP, LLC laboratories. Note that field sampling is most often outside the responsibilities of the laboratory. In such cases, the laboratory should clearly state that any estimates of uncertainty reported with samples relate only to analytical uncertainty.

• Transportation, storage and handling of samples

• Preparation of samples -all steps of the sample procedure prior to analysis. This can include variations in drying, grinding, filtering, weighings, dispensing of materials, extractant backgrounds, etc.

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MU Guidance Document


• Environmental and measurement conditions - those conditions that can impact some test results (e.g., gravimetry, microbiology) when they vary (e.g., temperature or humidity of the balance room, seasonal changes in microbiological background of micro labs, etc.).

• The personnel carrying out the tests -This is especially important with subjective tests such as microscopy and organism identification.

• Variations in the test procedure - for example, different recoveries for different batches of media, impurities in reagent lots, the effect of different extraction, digestion or incubation times and temperatures, percentages of microscopic samples read, etc.

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• The measuring instruments - variations in baseline drift, day to day calibration differences, carry over effects, interferences specific to the test method, microscope magnification used, etc.

• Calibration standards or reference materials - uncertainty related to reference materials or due to preparation differences, etc. Uncertainty estimates may come from certificates of analysis or estimations based on provider claims.

• Methods of generating test results - uncertainty due to data interpretation (e.g., peak integration, baseline manipulation, etc.), blank corrections, differences in how the software was used, other data manipulations, etc.

• Corrections for systematic effects - if test results are corrected for bias, include the uncertainty of the correction.

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– 5.4.1 Definition of the measurand.– 5.4.2 Identification of the contributors to

uncertainly.– 5.4.3 Details of the approaches used for

estimating measurement uncertainty, such as Type A and/or Type B.

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Basis of MU Policy/GuidanceKey Terms and Definitions

• type A evaluation of measurement uncertainty (VIM 2.28 JCGM 200:2008): evaluation of a component of measurement uncertainty by a statistical analysis of measured quantity values obtained under defined measurement conditions

• NOTE 1 For various types of measurement conditions, see repeatability condition of measurement, intermediate precision condition of measurement, and reproducibility condition of measurement.

• type B evaluation of measurement uncertainty (VIM 2.29 JCGM 200:2008): evaluation of a component of measurement uncertainty determined by means other than a Type A evaluation of measurement uncertainty

• EXAMPLES Evaluation based on information• — associated with authoritative published quantity values,• — associated with the quantity value of a certified reference material,• — obtained from a calibration certificate,• — about drift,• — obtained from the accuracy class of a verified measuring instrument,• obtained from limits deduced through personal experience.

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When using the Type A approach, laboratories shall utilize one or more of the following options. These options are generally considered from 1) most suitable, to 4) least suitable:

• 1) Uncertainty specified within a standard method. In those cases where a well-recognized test method (such as a peer-reviewed AOAC, NIOSH, OSHA, ASTM, etc. method), specifies limits to the values of the major sources of uncertainty of measurement and specifies the form of presentation of calculated results, laboratories need not do anything more than follow the reporting instructions as long as they can demonstrate they follow the reference method without modification and can meet the specified reliability.

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• 2) Laboratory Control Samples (LCS) and Matrix Spikes. In cases where matrix specific LCS (CRM or media spikes) and/or matrix spike data are available, include uncertainty estimated from the standard deviation of long term data collected from routine sample runs for existing test methods or from the standard deviation of the LCS or matrix spike data for method validation/verification studies for new test methods.

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• 3) Duplicate Data. In cases where sub-sampling occurs and there are data over the reporting limit, include uncertainty estimated from long term duplicate data collected from routine sample runs for existing test methods or method validation/verification studies for new test methods.

• 4) Proficiency Testing (PT) Sample Data. In cases where the previous options are not available and where PT samples are analyzed with sufficient data above the reporting limit, pooled PT sample data can be used to estimate uncertainty.

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5.4Laboratories shall have a written procedure describing the process used to estimate measurement uncertainty, including at a minimum:

• 5.4.4 Identification of the contributors of variability

for qualitative test methods.

• 5.4.5 All calculations used to estimate measurement uncertainty and bias.

• 5.4.6 The reporting procedure.

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• 5.5 Laboratories are required to re-estimate measurement uncertainty when changes to their operations are made that may affect sources of uncertainty.

• 5.6 Laboratories shall report the expanded measurement uncertainty, along with the reported analyte concentration, in the same units as analyte concentration, when:

– • it is relevant to the validity or application of the test results, or

– • a customer's instructions so requires, or

– • the uncertainty affects compliance to a specification limit.

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• 5.7 When reporting measurement uncertainty, the test report shall include the coverage factor and confidence level used in the estimations (typically k = approximately 2 at the 95% confidence level).

• 5.8 When the test method has a known and uncorrected systematic bias, it shall be reported separately from the test result and uncertainty estimation, as a probable bias value

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• Expanded uncertainty (VIM 2.35 JCGM 200:2008): product of a combined standard measurement uncertainty and a factor larger than the number one

• NOTE 1 The factor depends upon the type of probability distribution of the output quantity in a measurement model and on the selected coverage probability.

• NOTE 2 The term “factor” in this definition refers to a coverage factor.

• NOTE 3 Expanded measurement uncertainty is termed “overall uncertainty” in paragraph 5 of Recommendation INC-1 (1980) (see the GUM) and simply “uncertainty” in IEC documents.

• combined standard uncertainty (VIM 2.31 JCGM 200:2008): standard measurement uncertainty that is obtained using the individual standard measurement uncertainties associated with the input quantities in a measurement model

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• coverage factor (VIM 2.38 JCGM 200:2008): number larger than one by which a combined standard measurement uncertainty is multiplied to obtain an expanded measurement uncertainty

• NOTE: A coverage factor, k, is typically in the range of 2 to 3.

• standard uncertainty (VIM 2.30 JCGM 200:2008): measurement uncertainty expressed as a standard deviation

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Summary of Guidance Document Steps

• Review and identify the contributors

• Determine if contributors are accounted for with existing QC data

• Compile the applicable QC data and any other contributors and perform calculation of combined uncertainty

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• Combined uncertainty

SDc = √ [ SD12 + SD2

2 + … + SDn2 ]

It may be beneficial to use RSD instead of SD as it allows for the concentration dependence of SD.

NOTE: Sources that have an SD of less than 1/3 of the largest SD can be eliminated

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• Calculate the expanded uncertainty

– Apply the appropriate coverage factor 'k'. Calculate the expanded uncertainty by multiplying the combined standard uncertainty by the appropriate coverage factor (k) to give an expanded uncertainty with the desired confidence level. The factor k is the confidence interval Student distribution t-factor for n-1 degrees of freedom. For a confidence level of 95%, k is approximately 2 for a data set of 30 points or more, for normally distributed data sets.

– Expanded measurement uncertainty = k x SDc

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• Reporting test results with the expanded measurement uncertainty– Total benzene concentration of 88 ug/sample + 11

ug/sample at the 95% confidence level (k=2).

• Where bias is present, report it along with the uncertainty as a probable bias in a manner such as the following example:– Total lead concentration of 78 ug/sample + 12 ug/filter at

the 95% confidence level (k=2). This method has an average recovery of 94%, or at this level, a probable bias of -5 ug/filter.

• Alternate forms of reporting uncertainty and bias are acceptable as long as required information is clearly presented.

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6. ASSESSMENT FOR ACCREDITATION

• During assessment and surveillance of a laboratory, the assessor will evaluate the capability of the laboratory to estimate the measurement uncertainty for test methods included in the laboratory’s scope of accreditation. The assessor will verify that the methods of estimation applied are valid, all significant contributors to uncertainty have been considered, and all the criteria of the AIHA-LAP, LLC policy are met.

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Guidance and Examples

• Refer to the AIHA-LAP, LLC Guidance on the Estimation of Uncertainty of Measurement for suggestions and examples for implementing the policies and helpful references.

• Example Excel spreadsheets also on the website

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“Example Chemistry Measurement Uncertainty Calculations” workbook includes:

• Common Contributors to Measurement Uncertainty

• Example contributors and calculations for Chromatography

• Example contributors and calculations for Lead in Paint

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“Example Microbiology Measurement Uncertainty Calculations” workbook includes:

• Example contributors and calculations for Direct Examination Air

• Example contributors and calculations for culturable analyses (fungal swabs)

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Summary of Requirements

• Section 5.1 requires laboratories to be able to calculate an estimated measurement uncertainty, when requested, for all quantitative test methods covered by their AIHA LAP, LLC accreditation.

• Section 5.2 requires laboratories to treat each significantly different matrix (e.g., filters vs. bulks) separately when estimating

measurement uncertainty.

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• Section 5.3 addresses qualitative test methods. For these methods, laboratories are only required to understand the contributors to variability of test results and attempt to minimize them.

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• Section 5.4 requires laboratories to have a written procedure describing how they estimate measurement uncertainty.

Procedures must define the measurand, identify contributors to uncertainty, detail the approach that will be used to make the measurement uncertainty estimation, identify the calculations to be used to estimate measurement uncertainty and bias, and define how the information will be reported when required.

Types of QC data that may be used in making the estimates are identified.

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• Section 5.5 identifies conditions that will require laboratories to re-estimate measurement uncertainty of a test method.

• Section 5.6 defines when and how measurement uncertainty, as expanded

measurement uncertainty, shall be reported.

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• Section 5.7 requires the coverage factor used and confidence level to be included when reporting measurement uncertainty.

• Section 5.8 identifies requirements for reporting bias when it is known and a correction for it has not been applied to the reported result.

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Beginning April 1, 2010

• Your procedures must include all elements in Section 5 of the AIHA-LAP,LLC measurement uncertainty policy.

• The procedures must be implemented.

• All contributors to MU must be considered and dealt with in a defensible manner.

• The calculations must make sense.

• Your lab must have the ability to report MU, even if the customer is currently not requesting it.

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Questions?

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Traceability Documents

• Appendix H

– Policy on Traceability of Measurement (Rev. 0, effect. April 1, 2010)

• Guidance on Traceability of Measurement (Rev. 1, 2/17/10)

• CALA Example Internal Calibration Workbook

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Policy on the Traceability of Measurement

(Traceability Policy)

• 1. Scope

• 2. References

• 3. Terms and Definitions

• 4. Background

• 5. Policy

• 6. Guidance on Implementing this Policy

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Basis of Traceability Policy

References

• ISO/IEC 17025:2005 - General Requirements for the Competence of Testing and Calibration Laboratories

• ILAC-P10 Policy on Traceability of Measurement Results

• ILAC-G24 Guidelines for the determination of calibration intervals of measuring instruments

• CALA A61 CALA Traceability Policy (CALA)

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4. BACKGROUND

Traceability is characterized (in ILAC documents and the VIM) by 6 basic requirements:

• (a) an unbroken chain of comparisons going back to stated references acceptable to the parties, usually a national or international standard;

• (b) uncertainty of measurement; the uncertainty of measurement for each step in the traceability chain must be calculated or estimated according to agreed methods and must be stated so that an overall uncertainty for the whole chain may be calculated or estimated

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4. BACKGROUND

Traceability is characterized (in ILAC documents and the VIM) by:

• (c) documentation; each step in the traceability chain must be performed according to documented and generally acknowledged procedures; the results must be recorded;

• (d) competence; the laboratories or bodies performing one or more steps in the traceability chain must supply evidence for their technical competence (e.g. by demonstrating that they are accredited for that activity);

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4. BACKGROUND

Traceability is characterized (in ILAC documents and the VIM) by:

• (e) reference to SI units; the chain of comparisons must, where possible, end at primary standards for the realization of the SI units;

• (f) calibration intervals; calibrations must be repeated at appropriate intervals; the length of these intervals will depend on a number of variables (e.g. uncertainty required, frequency of use, way of use, stability of the equipment).

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4. BACKGROUND

AIHA-LAP, LLC accredited laboratories must understand the following simple relationship. All three of these components must exist at every level in the traceability chain in order for the final test result to be traceable.

Calibration (1) with Uncertainty (2) produces a measurement result that is Traceable (3)

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Basis of Traceability Policy/Guidance

Requirements• ISO/IEC 17025, Clause 5.6

– 5.6.1 – All equipment used for tests and/or calibrations, including equipment for subsidiary measurements (e.g. for environmental conditions) having a significant effect on the accuracy or validity of the result of the test, calibration or sampling shall be calibrated before being put into service. The laboratory shall have an established programme and procedure for the calibration of its equipment.

– 5.6.2 – specific requirements for calibration and testing

– 5.6.3 – reference standards and reference materials

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5. AIHA-LAP, LLC TRACEABILITY OF

MEASUREMENT POLICY

• The requirement which underlies this policy is given in ISO/IEC 17025, Clause 5.6.

• 5.1 Laboratories accredited by AIHA-LAP, LLC shall demonstrate, when possible, that calibrations of critical equipment and hence the measurement results generated by that equipment, relevant to their scope of accreditation, are traceable to the SI through an unbroken chain of calibrations.

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MEASUREMENT POLICY

• 5.2 External calibration services shall, wherever possible, be obtained from providers accredited to ISO/IEC 17025 by an ILAC recognized signatory. Calibration certificates shall be endorsed by a recognized accreditation body symbol. Certificates shall indicate traceability to the SI or reference standard and include the measurement result with the associated uncertainty of measurement.

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MEASUREMENT POLICY

• 5.3 Where traceability to the SI is not technically possible or reasonable, the laboratory shall use certified reference materials provided by a competent supplier (refer to ISO/IEC 17025 4.6.4), or use specified methods and/or consensus standards that are clearly described and agreed to by all parties concerned. A competent supplier is an NMI or an accredited reference material provider (RMP) that conforms with ISO Guide 34 in combination with ISO/IEC 17025, or ILAC Guidelines for the Competence of Reference Material Producers, ILAC G12. Conformance is demonstrated through accreditation by an ILAC recognized signatory.

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MEASUREMENT POLICY

• NOTE: There are many gaps in the measurement traceability of the calibration infrastructure in the world and there are a relatively small number of accredited reference material providers. In recognition of this situation, AIHA-LAP, LLC will not require the use of accredited reference material providers, where applicable, until January 2012. AIHA-LAP, LLC assessors will, at present, note any nonconformity with this requirement of Section 5.3 of this policy as a suggestion for improvement.

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MEASUREMENT POLICY

• 5.4 Reference materials shall have a certificate of analysis that documents traceability to a primary standard or certified reference material and associated uncertainty, when possible. When applicable, the certificate must document the specific NIST SRM® or NMI certified reference

material used for traceability.

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MEASUREMENT POLICY

• 5.5 Calibrations performed in-house shall be documented in a manner that demonstrates traceability via an unbroken chain of calibrations regarding the reference standard/material used, allowing for an overall uncertainty to be estimated for the in-house calibration.

• 5.6 Calibrations shall be repeated at appropriate intervals, the length of which can be dependant on the uncertainty required, the frequency of use and verification, the manner of use, stability of the equipment, and risk of failure considerations. Table 5-1 provides the minimum frequencies that are required.

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MEASUREMENT POLICY

• 5.7 Periodic verifications shall be performed to demonstrate the continued validity of the calibration at specified intervals between calibrations. The frequency of verifications can be dependent on the uncertainty required, the frequency of use, the manner of use, stability of the equipment, and risk of failure considerations. Table 5-1 provides the minimum frequencies that are required.

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MEASUREMENT POLICY

• 5.8 The laboratory shall have procedures describing their external and internal calibration and verification activities and frequencies, and the actions to follow if the equipment is found to be out of acceptable specification.

• 5.9 Laboratory staff performing in-house calibrations and verifications shall have received documented training.

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Table 5-1 Minimum Calibration/Verification Frequency Requirements for

Common Reference Standards and Support Equipment Reference Standard / Equipment Calibration Frequency Verification Frequency

Reference Thermometer Initial and every 5 years Not applicable

Working Thermometer Initial and when verification fails Annually

Reference Masses Initial and every 5 years Not applicable

Working Masses NA Initial and then annually

Stage Micrometer Initial and if damaged Not applicable

Balance Initial and following service/repair or when verification fails

Each day of use

Mechanical Pipettes Initial and when verification fails Annual

Volumetric Containers for critical functions (non-Class A)

Not applicable Each lot prior to use

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Table 5-1 Minimum Calibration/Verification Frequency Requirements for

Common Reference Standards and Support Equipment

• NOTE: It is imperative laboratories understand that this table is not a list of recommended frequencies. Rather, they are the minimum frequencies that will be accepted by AIHA-LAP, LLC assessors. It is the laboratory’s responsibility to establish a suitable schedule.

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Guidance Document and Examples

• Refer to the AIHA-LAP, LLC Guidance on the Traceability of Measurement for suggestions and examples for implementing the policies and helpful references.

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Guidance Document Includes:

• Information to help determine what equipment needs calibration or verification and the frequency at which these are needed.

• Important considerations when purchasing reference standards and calibration services, including content of calibration certificates.

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Guidance Document Includes:

• Considerations when performing in-house calibrations and verifications of various types of analytical instruments and support equipment.

• Tables listing Uncertainty Contributors when calibrating balances, thermometers and pipettes.

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Uncertainty Contribution Table for Thermometers

Contribution (nomenclature)

Distribution

Estimated Value

urStandard uncertainty

of the nominal values of the reference thermometer.

Normal Expanded uncertainty on the calibration certificate of the reference thermometer divided by 2 (coverage factor – k)

spStandard deviation of

the set of calibration readings

Normal Standard deviation of the set of calibration measurements.

u

1

Standard uncertainty of the readability and resolution of the working thermometer

Uniform (Square)

Smallest gradation of the working thermometer divided by √3. Use ONLY if Sp = 0

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Uncertainty Contribution Table for Pipettes


Distribution

Estimated Value

ur Standard uncertainty of the nominal values of the reference balance.

Normal Expanded uncertainty on the calibration certificate of the reference balance divided by 2 (coverage factor – k)

Sp Standard deviation of the set of calibration readings

Normal Standard deviation of the set of calibration measurements.

STStandard deviation of

corrections caused by temperature (∆T) when the temperature differs from standard temperature (20oC). The thermal coefficient of expansion of water is 0.00021 per 1° Celsius at 20° Celsius.

Uniform (Square)

Relative Standard Deviation = (∆T x 0.0002) / (√3) in millilitres per millilitre

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Uncertainty Contribution Table for Pipettes


Distribution

Estimated Value

u1 Standard uncertainty of the readability and resolution of the working volumetric instrument

Uniform (Square)

Smallest gradation of the working volumetric instrument divided by √3. Use ONLY if Sp = 0

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Additional Guidance Document Content

• Guidance on how to find an ILAC recognized accredited calibration laboratory.

• Guidance on selecting reference material providers, including sources for identifying those that are ILAC recognized.

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Example Excel calibration worksheets are also found on the AIHA website.

Key concept to remember: traceable calibration must also include uncertainty.

• Calculate the combined uncertainty

SDc = √ [ SD12 + SD2

2 + … + SDn2 ]

• Calculate the expanded uncertainty

Apply a coverage factor ‘2'.

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Summary of Traceability Policy

• Section 5.1 requires laboratories to demonstrate, when possible, that their analytical results are traceable to the SI (International System of Units) through an unbroken chain of calibrations within the measuring system. This requirement can be met for weights (masses), balances, thermometers, volumetric ware (e.g., mechanical pipettes) and stage micrometers.

• Section 5.2 expands upon the required information that must be included in calibration certificates received from accredited external calibration services.

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• Section 5.3 details requirements for providing traceability of analytical results when traceability to the SI is not possible (most chemical and microbiological analyses). Included are requirements for providers of reference materials. Because there are currently only a few accredited reference material producers, use of these producers will be encouraged where available but not mandated until 2012. Traceability options using specified methods or consensus standards are also provided.

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• Section 5.4 requires certificates of analysis for reference materials and defines information that is required on the certificates.

• Section 5.5 addresses documentation required for

in-house calibrations and requires these calibrations to include an estimation of the overall measurement uncertainty.

• Section 5.6 requires laboratories to establish the

frequency at which calibrations will be repeated. A table of minimum calibration frequencies for reference standards and support equipment is included.

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• Section 5.7 requires laboratories to also establish a frequency for and perform calibration verifications to demonstrate the continued validity of the calibrations. A table of minimum verification frequencies is provided

• Section 5.8 requires laboratories to have procedures that describe internal and external calibration and verification activities and their frequencies. These procedures must also describe the actions to be taken if equipment is found to be performing outside of acceptable specifications.

• Section 5.9 requires laboratories to maintain documentation demonstrating that personnel who perform in-house calibrations and verifications have been trained to perform these activities.

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As of April 1, 2010

• Traceability procedure(s) must include all elements from the AIHA-LAP, LLC policy.

• The procedure(s) must be implemented.

• All equipment must be considered and those with a significant impact on test results should be dealt with in a defensible manner.

• The calculations used follow the MU policy

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Next Steps

• .25 CM points were granted for the March 11 MU and Traceability Webinar– Will also apply for CM points this Webinar

• We are collecting questions from both Webinars with the goal of developing a FAQ to post on the AIHA-LAP, LLC website in late June.

• Thank you for participating!

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Questions?

1 aiha-lap, llc webinar measurement uncertainty and traceability policies review friday, april 30,...

Documents

measurement mu policy

uncertainty of measurement

llc uncertainty policy

estimation of uncertainty

previous guidance

new mu

policy documents

traceability documents