PT Protocol- General Information
This PT protocol is a part of Information brochure on PT Scheme(s) and is in public domain
(www.greenalliance.in). PT Protocol provides general information, on how PT Schemes are run, read along with PT Calendars and Registration Form ¶ Terms & Conditions for participation ¶ PT Protocol ¶ Frequently asked questions ¶ Accredited Scope as per ISO/IEC 17043. Participants are informed if there is any specific change in running a PT Round then described in the protocol.
For symbols, abbreviations/acronyms refer to end of protocol. In this protocol use of “masculine” gender shall include the “feminine” gender and “singular” shall include “plural” wherever relevant to the context, and vice versa.
PT Provider Location:
Envirocare Labs Pvt. Ltd. PT Cell
Enviro House, A7-A8, MIDC Main Road,
Wagle Estate, Thane Maharashtra, India 400604
Contact Information:
M: +91-9167702413
PURPOSE AND SCOPE OF PROFICIENCY TESTING:
ELPT conducts quantitative and or qualitative or interpretive or sampling PT Schemes/PT Rounds; single or continuous; simultaneous; pre-analytical, analytical or post-analytical for evaluation of participant performance against pre-established criteria by means of interlaboratory comparisons in line with requirements of ISO/IEC 17043: 2023, ISO 13528:2022, customers, regulatory authorities and organizations providing recognitions (NABL).
EXTERNALLY PROVIDED PRODUCTS AND SERVICES:
PT Provider does not use external service providers for the following activities (a) the design and planning of PT Schemes (b) the evaluation of performance (c) the authorization of reports. However, as and when required ELPT may use Advisory Group / Technical Experts while conducting different PT Schemes. ELPT purchases services and supplies including materials required for preparing the PT Items, consumables, reference materials, equipment’s that affect the quality of its PT Schemes from authorized reputed / registered vendors only. ELPT uses competent In-house laboratory for testing carried out for the purpose of homogeneity or stability assessment or for assigning the property values (NABL 181A).
IMPARTIALITY
PT Provider ensures:
• PT Activities including performance evaluation of participants are conducted without any bias.
• Performance evaluation of participants and the validity of the PT Scheme are not compromised due to being influenced by any relationships.
• Arrangements are made to prevent collusion or falsification of results (Refer Terms and conditions also)
• When a relationship poses unacceptable threat to impartiality, PT services are not provided
• PT Items are prepared, handled and distributed by authorized person / agencies.
• The access to the records of communication, codification and distribution of PT Items are controlled.
• PT Provider has provisions to get photographs, videos, and participants’ original observation data of test or measurement conducted on PT Item.
CONFIDENTIALITY POLICY
- Identity of customer or participants is kept confidential by unique coding and is known only to persons involved in operation of PT Scheme. Participants may be given the same code number in different PT Scheme by chance. ELPT has a continuing obligation to identify and report any actual or potential conflicts of interest arising during the operation of the PT Scheme. If an actual or potential organizational conflict of interest is identified, ELPT will immediately make a full disclosure to the appropriate parties and actions to eliminate or minimize risks to confidentiality and to maintain confidentiality
- The information provided by customer or participants to PT Provider is kept confidential including any information created during PT Activities:
- When PT Provider is required by law or authorized by contractual arrangements to release confidential information, the consent of participating laboratory is taken, unless prohibited by law except the records of PT Scheme participation are accessible to NABL. Results are also shared with regulators where asked by them. Results may also be shared with the customer for which a PT Scheme is provided through a contractual arrangement for its participants.
- Participants can also be asked to waive of confidentiality within the PT Scheme for the purpose of discussion and mutual assistance or as required due to very nature of PT Scheme
- PT Provider shares documents and records with organizations providing recognition e.g. NABL as part of its audit or assessment requirements.
- PT Provider may use data and experience from operation of PT Schemes for the purpose of further developments including, but not be limited to, use for research publications or conferences, PT Conclaves, however, identity of participants is kept confidential
- The identity of any external service Provider used is not disclosed in report or otherwise to ensure confidentiality
- Information about a customer or participant from a source other than participant or customer is kept confidential by PT Provider. The identity of the source is kept confidential by PT Provider and is not shared with the customer or participant unless agreed by the source.
PARTICIPATION IN A PT SCHEME:
ELPT tries it best to provide PT Schemes and incorporate parameters to deliver optimum solutions to CABs in terms of cost without compromising quality.
For criteria to be met for participation, refer to Terms and Conditions. For latest PT Calendars refer to the ELPT website www.proficiencytesting.in providing following information Organization Name and
Submission of registration form may be exempted by PT Provider at its sole discretion under any special circumstances as deemed fit by PT Provider and registration may be accepted via other means as request on email, work order etc. The decision of PT Provider is final in this regard. Registration is on first cum first basis. Participants who register late may be shifted to next PT Round. PT Provider may suggest/ request for participation in a specific scheme for meeting the minimum participants requirement or otherwise. PT Provider may also restrict participation depending upon the nature of the scheme and issues related to availability of infrastructure support or any other issues specific to the scheme.
Registration for a scheme closes on the date of registration mentioned in PT Calendars unless the scheme is extended. However, PT provider can admit participants who fail to register by the given deadline and may allow registration as long as sample preparation has not started or extra samples can be provided from the lot. The decision of PT provider is final in this regard.
Participation in the PT scheme is given in good faith. PT Provider may refuse provision of PT Services to the customer or participant in case of influencing/ canvassing/ threatening/ disrespectful behaviour/ use of abusive language/ proven evidence of fraudulent behaviour/ suspected collusion or issues affecting impartiality, confidentiality and integrity / pending payments / harassment / business conflicts / nuisance / misuse and or theft of reports, data and information, plagiarism. PT provider may forfeit any payments made for PT purpose in such scenarios and decision of PT provider shall be final. Further, if it is found that any participant is misusing registration or making any other false claims to meet the requirements of accreditation or regulatory bodies and subsequently drop their registration or do not respond or does not make payments, the PTP has a right to bring the same to the notice of the concerned accreditation or regulatory body or customer and disclose the identity of such participant including taking any other appropriate action as deemed fit.
Where customer (e.g. a consultant) is coordinating PT for a group of laboratories; it is limited to making payments on behalf of laboratories or coordinating other administrative issues or request for a special
Scheme say covering additional parameters, however, beyond that each laboratory has to register individually and any communication related to PT activities is done with laboratories only unless agreed otherwise.
Minimum number of participants for running a Quantitative PT Round are four or more and for Qualitative PT scheme it is two or more. When minimum 8 or more participants are available. For Quantitative/Qualitative PT Round if less than 4 participants are there the evaluation shall be done using assigned value determined by method other than using ‘consensus value of participants’. Both accredited and non-accredited participants meeting requirements of NABL-142 are eligible for participation. If a laboratory is not meeting the requirements of NABL 142, it is labs responsibility to inform the PT Provider at the time of registration. PT Provider may allow participation to such participants, however, additional measures as laid down in PT Plan/Design are taken to ensure performance evaluation is meaningful.
FEES:
Refer to PT Calendar. PT calendar is to be treated as a quotation. Fixing/Charging of fees including providing any discounts is a sole prerogative of PT Provider.
PROFICIENCY TEST ITEMS:
PT Scheme Plan/Design discusses selection of the measurand(s)or characteristic(s) of interest, including information on what the participants are to identify, measure, or test or sample in the specific PT Scheme as well as description of the range of values or characteristics, or both, to be expected for the PT Items.
Relevant information is available to participants initially in PT Calendars. Registered participants are provided all relevant information subsequently in detail during the operation of the PT Scheme.
The determinants in PT Items may either be at natural levels, incurred or spiked at a particular formulation level and or manipulated. The range of PT Items can usually be varied from round to round in order to be realistic and challenging.
Range is given only for limited guidance e.g. for an idea whether dilution will be required or not. It is varied to ensure that it is not used to guess the true value and sometimes may be used as a tool to avoid collusion or may not be provided. Laboratories should report the results as obtained by them irrespective of range given.
HOMOGENEITY AND STABILITY OF PT ITEMS:
Quantitative Properties
Homogeneity assessment is done prior to the distribution of PT Items among the participants and after the PT items are packed.
In this PT Round homogeneity assessment is done by selecting at random 10 PT Items in their final packaged form and analysing them in replicate by preparing two test portions and marking them as say IA, 1B, 2A, 2B,…… gA, gB. The homogeneity is ensured by establishing ss≤ 0.3 σpt. Cochran’s test is further undertaken to establish homogeneity as applicable.
Stability assessment is conducted after distribution of the PT items to the participants around the last date of submission of PT Results, preferably on or after the last date.
In this PT Round, stability assessment is done by selecting at random 2 PT Items in their final packaged form and analysing them in replicate by preparing two test portions and marking them as say IA, 1B,…… gA, gB. The stability is ensured by establishing Homogeneity Average (X)- Stability Average (Y) ≤ 0.3 σpt.
Qualitative Properties
Homogeneity assessment is done prior to the distribution of PT Items among the participants and after the PT items are packed.
In this PT Round homogeneity assessment is done by selecting at random 10% of PT Items prepared or 4 PT items (whichever is more) in their final packaged form and analysing them in replicate by preparing two test portions and marking them as say IA, 1B, 2A, 2B,…… gA, gB. The criterion for homogeneity assessment is that all PT Items selected for homogeneity assessment yield the same (expected) result.
Stability assessment is conducted after distribution of the PT items to the participants around the last date of submission of PT Results preferably on or after the last date.
In this PT Round stability assessment is done by selecting at random 2 PT Items in their final packaged form and analysing them in replicate by preparing two test portions and marking them as say IA, 1B,…… gA, gB. The criterion for stability assessment is that all PT Items selected for stability assessment yield the same (expected) result.
Further, in line with clause 6.1 of ISO 13528:2022 as documented in PT Design on case to case basis for subsequent Rounds, the number of PT Items included in homogeneity check may be reduced to g ≥4 or where a set of PT Items contain testing of multiple are used based on experience under repeatable conditions or on the basis of experience with the behaviour of closely similar PT Items in previous Rounds of the PT
Scheme verified as necessary for the current Round. As experience is gained, critical measurands in a Round may be analyzed only instead of all irrespective of replicates used. Also as experience is gained with regard to behaviour of a PT item the testing for homogeneity may be carried out after packing and distribution of
PT item to participants if so planned.
The aim is, however, to ensure that homogeneity and stability is fit for purpose and every participant receives comparable proficiency test Items.
In case of non-compliance, heterogeneity and or instability of the PT Items is considered for evaluating the performance of participants as per procedures. In these circumstances further explanation is given in the report and design is reviewed as applicable as certain PT Items may be heterogenous by nature.
PRODUCTION AND DISTRIBUTION OF PT ITEMS
While organizing the different Rounds of the PT Schemes, ELPT ensures that the matrix, properties, characteristics and concentration level of the PT Items are matching with the type of samples being regularly received by the testing laboratories. However, PT Items may be manipulated or be either at natural levels, incurred or spiked at a particular formulation level to ensure it is suitable for the purpose of evaluation.
In line with NABL-181A, PT Item supplied is sufficient for the analysis required once in order to ensure collusion does not happen. PT provider may issue additional PT item subject to its satisfaction of genuineness of the issue after due diligence. Decision of PT provider in this regard is final. The testing of PT
Items is not for the purpose of providing ‘statement of conformity’ as such number of PT Items to be tested may not necessarily be in line with requirements laid down to meet product compliance specifications.
Participants are advised to treat the PT Items similar to their routinely tested samples and carry out the testing and reporting of the same in accordance with their normal procedure. However, participants may be instructed to report the test results in a different manner for the purpose of performance evaluation by PT Provider in some cases.
REPORTING OF RESULTS:
Participants shall use methods as told in instructions given for ‘Handling and Analysis of PT Items’. Methods based on same or similar principle may also be used subject to be capable of achieving the measurement accuracy and/or measurement uncertainty required to provide a valid result. Please note PT Provider may, however, provide instructions to use specific amount of sample or condition a sample at particular temperature for a particular time to bring uniformity in handling on the basis of informed decision and as documented in PT Plan. If participant intends to use a method that is different from as given in instructions, participant should take prior permission in writing. PT provider may allow as per documentation in the PT Plan and provide relevant information including on performance evaluation to such participants.
Participant shall keep all technical or other records in line with requirements laid down in ISO/IEC 17025 for each activity related to participation in PT to facilitate audit trail (e.g. original data generated from analysis including any logged data, calculations, photographs, videos, status of calibration, use of reference materials etc.). PT Provider may or may not ask these records along with submission of PT Results. However, it is mandatory to provide such records in the stipulated time period whenever asked.
The failure of participant to provide said records or any other relevant information when asked by PT Provider may lead to ‘Results Not Considered’ / ‘Cancellation’ of participation. Decision of PT Provider in this regard shall be final.
Results reported in a semi-quantitative manner as “less than” or “more than” a value, or results reported as zero except where it may be appropriate to report a result of zero together with qualitative results or results not reported in ‘Result Submission Sheet’ provided by PT Provider or by tampering ‘Result Submission Sheet’ provided by PT Provider or results reported in units different from asked by PT Provider or if any desired information in ‘Result Reporting Sheet’ is left blank shall be collated and listed in the PT round report as ‘Results not Considered’ and shall not be included in the statistical analysis including any results that are tagged i.e. any comments are given. Participant shall resolve such issues with PT provider before submission of results. The decision of PT Provider shall be final in this case and no communications shall be entertained in this regard after the announcement of results. Summary of test results of participants as used by the PT provider are made available in draft result sheet. Draft result sheet is submitted only to verify that data read and entered by PT provider is correct and there are no readings or typing errors on PT provider’s part. The data values are, however, rounded to the decimal points as per standard practice laid down by IS e.g. if reporting decimal point (DP) asked is 2 and CAB report results as 23.445, then it is recorded 23.45 and if CAB reports as 23.444 then it is recorded as 23.44. No requests for any change in results are accepted except if there are typing and reading errors at PT providers end. Participants are asked to crosscheck and confirm in two days from the date of sending email and no claims are entertained later. PT provider does not provide draft result sheet or final report to participants who have not cleared the payment. In such a case, PT provider is not responsible if subsequently it is found that any results provided by participants are entered wrong due to lack of cross checking or otherwise.
For some parameters there may be large variation in test methods followed by CABs due to non-availability of standard methods or otherwise; in such scenario’s PT provider may provide specific instructions for the purpose of uniformity.
TIMELINE: Refer to terms and conditions of participation.
PREVENTION OF COLLUSION AND FALSIFICATION:
PT Provider builds a lot of measures in PT Round to try to prevent collusion. This may include but not limited to – The amount of PT item sent to participants is not too large; Manipulating ‘range’ for the purpose; Use of blind samples etc. Raw data, photographs and videos may also be asked. Participants are strongly advised not to engage in any collusion. Collusion is sole responsibility and risk of participant.
STATISTICAL ANALYSIS OF DATA:
The statistical analysis of data set is done starting with identification and removal of blunders by visual review as well as subjecting the data to any one of the following methods individually or in combination (i) Results that deviate from the X by more than ±5σpt or (ii) Outlier detection test such as Grubbs test (iii) presence of any obvious blunders or erroneous reporting in case of qualitative schemes based on literature, experience and any other relevant factors as laid out in PT Plan/Design. When any participant result is excluded then it is excluded only for the purpose of determination of xpt and σpt or other evaluation criteria.
Quantitative Schemes: After removal of blunders, PT Provider further uses robust estimators such as Algorithm-A in line with ISO 13528:2022 for the determination of both assigned value as well as σpt from the consensus value of participants when p ≥ 12 (after removal of outliers) as specified in Note 2 under D.1.2 of Annex D of ISO 13528:2022. When p < 12 (after removal of outliers) PT Provider uses other techniques as provided in ISO 13528:2022 and laid down in its procedure as median of the participants’ results or robust average from modified Algorithm-A. When z-score or z-prime score is determined as specified above, PT Provider ensures that participants identified as blunders are getting z-score or z-primes score ≥ ± 3.
Qualitative Schemes: Where assigned value is reported on a categorical (or nominal) scale, the assigned value determined by any of the methods should match exactly with the results obtained from homogeneity assessment. Where assigned value is reported on an ordinal scale, the assigned value determined by any of the methods should not differ by more than the permissible limit (that is used for performance evaluation of participants) with the results obtained from homogeneity assessment as provided in PT Plan/Design.
ASSIGNED VALUE, METROLOGICAL TRACEABILITY AND MEASUREMENT UNCERTAINTY OF ASSIGNED VALUE
Quantitative Properties
The standard uncertainty of assigned value u (xpt) is calculated using the following formula:
s*
u(xpt) = 1.25 x ———–
√p
The u (xpt) is compared with the following criteria to ensure compliance: u(xpt) ≤ 0.3 σpt. In case of non-compliance with the above criteria, performance evaluation is not done using z-score but using z’-score (z-prime) by taking into consideration the standard uncertainty of the assigned value also in the denominator.
The validity of the assigned value for measurands or characteristics of interest determined in PT Items is done by determining the estimate of the reference value of the PT Items determined independent of the participants results, xref (for example homogeneity average of the concerned measurand determined by an accredited CAB which is not a participant). The difference between homogeneity average and consensus average of participants is then calculated. The difference should be less than 2 times udiff where udiff = √ [ u (xpt)2 + u (xref)2]
Qualitative Properties
When the test results reported on categorical (nominal) scale, mode (most common observation) reported by participants is used as the assigned value or when the test results reported on ordinal scale (i) either mode (most common observation) or (ii) median reported by participants is used as the assigned value.
STANDARD DEVIATION FOR PROFICIENCY ASSESSMENT (σPT) and Performance Evaluation:
Quantitative Properties
In this PT Round, σpt is determined from the consensus values of participants.
Where p ≥ 12 as specified in Note 2 under D.1.2 of Annex D of ISO 13528:2022 Algorithm-A is used to determine σpt (Annex C ISO 13528:2022). Where p < 12 but ≥ 4 PT Provider uses Formula D.1 ‘Mean Absolute Deviation from Median Method’ (Annex-D ISO 13528:2022) to determine σpt
Performance evaluation is done in terms of z-score which is calculated using the following formula:
(xi – xpt)
z-score = ————- (1.5.1)
σpt
When u(xpt) is not meeting the criteria: u(xpt) ≤ 0.3 σpt. performance evaluation is done using z’-score (z-prime) by taking into consideration the standard uncertainty of the assigned value also in the denominator:
(xi – xpt)
z’-score = ————————- (1.5.2)
√ [ (σpt)2 + u (xpt)2]
In line with ISO 13528:2022 clause 8.6.2 and as laid down by organization providing recognition in order to ensure that σpt used for performance evaluations is fit for purpose including ensuring fitness with reference to lower and upper limits placed on σpt, PT Provider uses σpt by perception for measurands marked with $ in statistical data and summaries (1.7)
It is possible for the z-scores published in this report to differ slightly from the z-score that can be calculated using the formula given above. These differences arise from the necessary rounding of the data prior to its publication in report.
The following interpretation is given to results
| Result | Interpretation | Coding |
| |z/z’Score| ≤ 2.0 | Satisfactory result | Black |
| 2.01 < |z/z’ Score| <2.99 | Questionable result (straggler) | Bold Black |
| |z/z’Score| ≥ 3.0 | Unsatisfactory result | Bold Red |
| — | No score RNS or RNC as explained | Black |
| Blunder | Obvious odd values as explained | B (Score) Bold Red |
Where |z| denotes the absolute value of the z-score. When an outlier is identified the sign of the z-score indicates whether the result is too high (positive z-score) or too low (negative z-score).
Qualitative Properties
In this PT Round for nominal data participant which has reported the result that exactly matches the assigned value is marked as ‘satisfactory’ (or scored as a success). Participant whose reported result does not exactly matches the assigned value is marked as ‘Unsatisfactory’ or given an adverse performance score. Proportion of participants whose results match the assigned value correctly is given in in statistical data and summaries (1.7).
No score is given for RNS. Results are taken as RNS, where participant may not submit results for a parameter(s) for various reasons- It is not in their scope or they have already covered that parameter(s) or participating only for outlier parameters or as per their plan will participate in parameter(s) in next Round or during testing is not confident of the results etc. PT Provider in this case does not give score and mark the score column as ‘–’. RNC are situations where participants report results as zero (except where results can be zero) or non-numerical results e.g. <0.1 or >1, Nil, BDL etc. or results are qualified by any symbol or given with any remarks etc.
FEEDBACK, APPEAL AND COMPLAINT
All due diligence is exercised in conducting the PT Round yet if a participant has any concern about any aspect of PT Round, they should contact undersigned within 15 days from the date of release of final report:
Quality Manager
Envirocare Labs Pvt. Ltd. PT Cell
M: +91-9167702413
Participants are encouraged to provide feedback for improving any aspect of the PT Scheme/ Round. Feedback form is sent along with the final report. An appeal can be made by a participant for reconsideration of any adverse decision. It is handled as per the documented procedure and appellant is provided with the outcome. If a complaint is received, it is handled as per the documented procedure and appellant is provided with the outcome.
USE OF PT REPORTS
The report or any other documents and records of PT Provider are strictly for use by customer or participant for (i) Participation in PT with PT Provider (ii) To monitor performance and or to improve the participants’ performance (ii) To show to relevant regulators and or organizations providing recognition as part of audit / assessment requirements. PT Report or any document or records in part or whole shall not be shared and or used by customer or participant to any individual or organization including its other divisions/sections for any reason other than as stated above without taking the permission of MD of PT Provider in writing. PT Provider can bar future participation for customer or participant if misuse or unauthorized sharing or use or tempering or copy paste of any records or documents of PT Provider is found. The customer may be provided with PT Report as applicable and agreed for a particular purpose.
DISCLAIMER
- This report is produced by PT Provider in good faith and in accordance with best industry practice. Neither Envirocare Labs Pvt. Ltd. (PT Provider) nor any individual or any other organization involved accepts any liability whatsoever from application or use of information contained therein or from any inadvertent error in the information in report including without limitation indirect or consequential loss or damage. This statement does not affect your statutory rights.
- Comments or recommendations in PT Report does not construe to be any legal or technical advice to participant. PT Provider is also not soliciting any action based on it. Any trade name given in this report is information given for the convenience of users and does not constitute as endorsement.
- The parties agree that any matters are governed by Indian law. All disputes are subject to original jurisdiction of Mumbai, India.
IMPORTANT
Participants are requested to go through all related documents in information brochure as PT calendar, registration form, terms and conditions for participation, NABL and clarify if there are any doubts any time including If there is any contradiction in details given in different documents under information brochure. All clarifications must be taken in writing on email, conclusions drawn from telephonic discussions are at participants own risk. Typographical and clerical errors are subject to correction.
| Symbols | |
| di | Difference between measurement value for PT Item and an assigned value for a CRM |
| D | Participant difference from assigned value x – xpt |
| D% | Participant difference from assigned value expressed as percentage of xpt |
| ẟE | Maximum permissible error criterion for differences |
| ẟhom | Errors due to difference between PT Items |
| ẟstab | Errors due to instability during the period of PT Items |
| ẟtrans | Errors due to instability during under transport conditions |
| g | Number of PT Items tested in homogeneity checks |
| m | Number of replicate measurements to be made on a PT Item |
| p | Number of participants taking part in round of PT Scheme |
| sr | Estimate of repeatability standard deviation |
| sR | Estimate of reproducibility standard deviation |
| ss | Estimate of between-sample standard deviation |
| s* | Robust estimate of the participants standard deviation |
| sx̄ | Standard deviation of sample averages |
| sw | Within-sample or within-laboratory standard deviation |
| σk | Bandwidth standard deviation used for kernel density plots |
| σL | Between laboratories (or participant) standard deviation |
| σpt | Standard deviation for proficiency assessment (SDPA) |
| σr | Repeatability standard deviation |
| σR | Reproducibility standard deviation |
| udiff | Standard uncertainty of the difference between an independent reference value or a robust average and an assigned value |
| Udiff | Expanded uncertainty of the difference between an independent reference value or a robust average and an assigned value |
| uchar | standard uncertainty due to characterization, |
| uhom | Standard Uncertainty due to difference between PT Items (Inhomogeneity) |
| umax | Upper limit of standard uncertainty used for screening participants reported MU |
| umin | Lower limit of standard uncertainty used for screening participants reported MU |
| ustab | Standard Uncertainty due to instability during the period of PT |
| utrans | Standard Uncertainty due to instability during transport conditions |
| u(xi) | Standard Uncertainty of a result from participant i |
| u(xpt) | Standard Uncertainty of the assigned value |
| u(xref) | Expanded Uncertainty of a reference value |
| U(xi) | Expanded Uncertainty of a result from participant i |
| U(xpt) | Expanded Uncertainty of the assigned value |
| U(xref) | Standard Uncertainty of a reference value |
| wt | Between test portion range |
| w* | Robust estimate of participant repeatability |
| X | Homogeneity Average |
| x | Measurement Result (generic) |
| xchar | Property value obtained from characterization (determination of assigned value) |
| xCRM | Certified value for a property in a CRM |
| xdiff | Difference between an independent reference value or a robust average and an assigned value |
| xi | Measurement result from participant i |
| xpt | Assigned value |
| xref | Reference value for a stated purpose |
| x * | Robust estimate of the participant mean |
| x̄ | Arithmetic average of a set of results |
| Y | Stability Average |
| Z | Score used for proficiency assessment (absolute value ±) |
| z’ | Modified z-score (commonly pronounced as z-prime) |
| Abbreviations / Acronyms | |
| ACV | Absolute compliant value |
| Amd. | Amendment |
| B | Blunder |
| BDL | Below Detection Limit |
| CRM | Certified Reference Material |
| CAB | Conformity Assessment Bodies |
| DP | Decimal places. This indicates number of figures in the value, counting from first figure after the decimal point and ending with the last figure on the right (IS 2: 2022) |
| e.g. | For example |
| et al. | Latin phrase et alia, which means “and others” |
| etc. | et cetra; and so on, and other things of a similar kind |
| ESP | Externally Provided Products and Service Providers / External Service Providers |
| ELPT | Envirocare Labs Pvt Ltd Proficiency Testing Cell |
| HDPE | High-density polyethylene |
| ISO | International Organization for Standardization |
| IEC | International Electro Technical Committee |
| MD | Managing Director |
| MPE | Maximum Permissible Error |
| NABL | National Accreditation Board for Testing and Calibration Laboratories (Organization providing recognition) |
| OPI | Overall Performance Index |
| Portable document format, used to display documents in an electronic form independent of the software, hardware or operating system they are viewed on. | |
| PS | Performance score |
| PT | Proficiency Testing |
| RNS | Results not submitted |
| RNC | Results not considered |
| SI | International System of Units |
| w.r.t. | with respect to |
Any other symbol or abbreviation used is described at the first instance. For more details including terms and definitions refer to ISO/IEC 17043:2023, ISO 13528:2022, ISO/IEC 17025:2017.