Ask the Standards Experts

Pesticide Residues Surveillance Program Sampling

ISO 14004, Environmental Management System, EMS

Question

I am plant production specialist working in government sector. I am the manager of pesticides residues surveillance program, on this program we targeting local commodities of fresh fruits and vegetables (F&V) by sampling the targeted numbers and types of F&V in regular basis around the year and we analyze samples and results and establish the annual report. I have checked many similar program in other countries included USDA program but I didn’t find approach methodology or statistical way to identify the sample size to be targeted in the year taking in account type and number of crops, crop production,…etc. to elaborate annual sampling plan. My question here is how can elaborate sampling plan for mentioned program considering all valuable factors?

Your cooperation is highly appreciated.

Answer

Sampling is a method to estimate population parameters. For example, if the goal is to determine the amount of unacceptable residue on store bought apples, and testing every individual apple is impractical, then we use a sample to estimate the proportion with unacceptable residue.

The sample plan must focus on the goal and balance with the resources and technology available. If the goal is to accurately detect a very low proportion with residue, say 1 in 1 million, then the sample size will be larger than if the goal is to detect 1 in 100 with unacceptable residue. The goal to detect 1 in 100 is easier to accomplish (fewer apples tested) yet does not reveal is there is a 1 in 1000 level or not.

A key element is the specific goal for detection and design a sample plan that is capable to detect at or better than the goal’s level. Capable includes the measurement system errors and an understanding of the nature of how failures occur.

Another consideration is the nature of the measurement and goal. If the test is only pass / fail for presence of residue, then we have to use the relatively inefficient sampling plans based on the binomial distribution. If the data is a variable value, such as part per million residue presence, then we can use more efficient sampling plans based on the appropriate continuous distribution. If the testing is destructive to the item being tested that limits the sampling techniques available.

How is the lot defined? If this is an annual report then the lot may be the annual production of a specific fruit or vegetable, say a specific variety of apples. Define the population clearly and any relevant subgroups of interest. If the data is only for an annual report the sampling plan is marked different than if the goal is a monthly monitoring and warning system.

Another consideration is the thresholds along with confidence. For sampling plan creation we use two specific points of interest. The Producer Risk Point (PRP) made up of the Acceptable Quality Level (AQL) and the producers’ risk (Type I risk or Alpha – which is the probability of rejecting a good lot, or in this case stating the residual level is above a specific AQL or value when it actually is not). The second point is the Consumer’s Risk Point made up of the Lot Tolerance Percent Defective (LTPD) and the consumer’s risk (Type II risk or Beta – which is the probability of accepting a bad lot, or in this case stating the residual level is below the LTPD when it is actually is not.)

The closer the AQL and LTPD are the more difficult (more samples) it is to determine an accurate estimate of the population. Likewise the less risk either the producer or consumer desire to incur again results in higher sample sizes.

One more consideration which is often overlooked is the selection of samples for testing. Most sampling plans are based on the assumption that the samples are taken randomly from the entire population. For example with say 50 million apples of a specific variety we would create a system to select samples that each has an equal change of any specific apply being selected. This is not a trivial matter in most cases. The availability and distribution of apples along with storage, shipping and display of apples all contribute to limited or biasing selecting a random sample. If it is not possible to select test items randomly, then study the impact on the study and means to account for a non-random sample.

In summary, for any sample plan:

Define the population
Define the desire goal of the study
Understand the measurement system
Use variables data if at all possible
Define PRP and CRP
Determine capable sampling plan
Design method to select random sample

This quick summary of consideration is what I consider the essential elements, yet other may impact the sampling plan. For example, seasonal variations in production, location in supply chain when measurements are made, variations in supply chain impact on presence of residual, differing nature of residue commonly found of different fruit or vegetables, and probably a few more. Understanding the goal, measurement system and random sampling will help determine areas that require consideration.

Cheers,

Fred Schenkelberg

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ISO/TS 29001:2010 Standard in Oil and Gas Production

Oil and gas industry, petroleum industry

Question:
We are an Oil & Gas production testing, frac flow back, and trucking company and while in the beginning stages of instituting ISO 9001:2008 standards, we ran across Oil & Gas industry specific standards ISO/TS 29001:2010 and we are curious as to whether or not we have to apply TS 29001:2010, ISO 9001:9008, and maybe some ISO standards for trucking to receive our ISO certification.

Response:
All of the TS should include ISO as the back bone with Industry specifics. The customers dictate which is required. For Auto Industry it is TS 16949 and for Aerospace AS9004. The technical specifications shall include ISO 9001 and the company is registered to the ISO with a TS. A little confusing but eliminates a vast set of international standards. The QMS is ISO 9001. I will always go on the side of using the industry specifics if that is the only industry that they work within as most TS requirements require the use of core tools. If you have these particular TS requirements I will review them but I very sure about this answer.

Ron Berglund
Global Quality Coach

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ISO/TS Standards Exclusions

Checklist, Conformity, Go/No Go

Question

I have a question regarding exclusions from the ISO/TS standards.

The majority of our business is the design and manufacture of enclosure hardware. Recently though, a small portion of our business has become the sole North American Distributor for an Italian company. Their product lines are similar to ours. However, we procure their products and simply resell/distribute to their customers stateside, to Canada and Mexico. We do not have Design or Process Control for these items; they are pass-through product.

Therefore, my question is related to permissible exclusions from the ISO standard. Should we seek exclusions regarding certain clauses of Clause 7 of the standard, for this certain “supplier”, and/or for certain product groups that are sold on their behalf?

Any assistance you could provide would be helpful.

Answer

Hello,

At first, your question seemed relatively uncomplicated and I am inclined to say that you can simply sell or provide the products in question with a disclaimer or something identifying the fact that your company is not the designer/manufacturer of the product. My company occasionally has purchased parts inserted into or added to the products made (like bushings or threaded inserts, etc). We don’t have to add anything to our QMS for those as long as those items meet regulatory and statutory requirements.

However, I should mention, the standards make it clear that exclusions are permissible if “such exclusions do not affect the organization’s ability or responsibility to consistently provide product that meets customer and applicable statutory and regulatory requirements.”

Therefore, stepping away from the initial ‘simple’ answer, I would say that such exclusions would not be permissible. This is due to the fact that your organization is ultimately responsible for meeting customer requirements. Although you do not design or manufacture that specific product, you provide, and are responsible for what the customer requests.

You are also responsible for seeing to it that the OEM is meeting customer as well as any statutory or regulatory requirements. This would be of particular importance if these are electrical enclosures or intended for hazardous services, such as NEMA 7 (explosion proof enclosures).

Since you already design and manufacture your own products and have the Clause 7 included in your QMS, it would be counterproductive to add more documentation to exclude what you have mentioned. It would be wise to notify customers up-front, in the sales/purchase order process, that the product you are distributing is from a separate company.

Thanks much for this good question.

Bud Salsbury
ASQ Senior Member, CQT, CQI

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Audit by Exception

Audit, audit by exception

Question:

I would like information regarding the use of the internal auditing method referred to as “audit by exception”. While this method sounds like it may provide a much more efficient use of my time and my Manager’s/employees time, I have no idea how this is accomplished in a manner that can still be compliant and what proof would be deemed acceptable when going through my external RAB certified audit. I am referring specifically to ISO 9001:2008 in regards to auditing. I currently audit every process/process owner every 6 months in a calendar year and it is a full week of audit time each audit. Thank you.

Response:

Thanks for contacting ASQ’s Ask the Expert program. With regard to your inquiry, I suggest that you continue to use an audit methodology that best serves your organization’s requirements. As you are aware, “auditing by exception”, is a practice that is utilized in the financial sector. The terminology “audit exception” in this case, has the same meaning as an “audit finding”. Since internal audits are one of the most important tools that an organization has to assess the effectiveness and continual improvement their quality management system, auditing by exception may not provide the level of information needed to keep your organization’s top management and it’s process owners adequately informed.
In my opinion, an effective internal audit will focus as much on identifying opportunities for improvement (OFI) as documenting audit findings. A robust internal audit report will identify nonconformances, but will equally focus on areas that can be improved or that have improved. To sustain continual improvement of a new or a matured QMS, the process owners and employees must be kept informed and engaged. One of the ways to accomplish this, is to share audit results that report on findings, OFI and the status of objectives or targets that have been established. Auditing by exception, usually will not provide this level of reporting.

Please note, ISO 9001:2008, clause 8.2.2, does not prescribe any particular audit methods to be used for 1st, 2nd or 3rd party audits. Each organization is expected to select audit techniques that best suit the scope and objective of the audit to be conducted.

I hope this helps.

Best regards,

Bill Aston, Managing Director
Aston Technical Consulting Services
Kingwood, Texas

ISO 9001:2008 Requirement for Control and Monitoring of Measurement Equipment

Chemistry, micro testing, chemical analysis, sampling

Inquiry

I am trying to clearly understand the ISO 9001:2008 requirement for Control and Monitoring of Measurement Equipment. My question:

If a measurement equipment like a Karl Fisher Titrator or pH meter which is calibrated by the user with a known standard traceable to an international standard, then does the unit itself require to be periodically sent to a third party for calibration? It is not clear to me. In the past I have received a finding for not doing so. As I read the standard it is not clear. Can you provide exactly the clause and reference statement that would indicate and clarify its meaning.

Response:

Your question leads me to believe there was a valid reason for the finding you received. Calibration of a Karl Fischer Electrometric Titration unit is more of a validation and adjustment. That is, in one common practice, you use sodium tartrate dehydrate in a very fine powder form, along with other substances and follow all the steps of calibration. However, (this is why sending your unit to a third party becomes necessary), you cannot be certain your unit is reading accurately if it hasn’t had a certified calibration by a third party. Example: Is the water equivalent (WE) of the titrant (Karl Fischer reagent or titrating solution) based on accurate calculations?

If you have a known standard which is traceable to national standards which you can use as a comparator, you might be able to set your recalibration periods fairly far apart. This would of course save you money. Nonetheless, unless you can show traceability of your Karl Fischer system, you are not compliant with the standard.

That was a good question and I hope this will help.

Bud Salsbury, CQT, CQI

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Measurement System Analysis

ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories

Question:

Is there ever an exception to the rule about needing full Measurement System Analysis for any instrument placed in the Evaluation / Measurement Technique column on the Control Plan? If an instrument is listed on the control plan, does it HAVE to have GRRs done, in addition to having to prove stability? Please base off of ISO 9001 and TS 16949 requirements, and if there is a difference between them for this requirement.

Answer:

Thank you for this interesting question. Clause 7.6 of ISO 9001: 2008 makes most of this fairly clear. Any monitoring and measuring equipment used to verify conformity of product must “be calibrated or verified, or both, at specified intervals, or prior to use. . .” Notice I made ‘at specified intervals’ bold. This is just to bring to light the importance of calibration cycles. You/your organization can determine what those cycles will be based on the stability of the measuring tool, frequency of use, working conditions, etc. For example, if you were using a micrometer to check close tolerance parts and, you found it a good process to measure the parts frequently, this would be a contributing factor to the decision process. Then, if the working conditions included a lot of cutting fluids or perhaps a good deal of metal dust, another factor is added to the decision process. What I am driving at is this; once you have determined that the product conformity which you are checking is good and/or consistent and that your sample frequency is satisfactory, you would have no definite requirement for GRR’s on the measuring equipment. The calibrations and or verifications you do must be with equipment which is traceable to international or national measurement standards. If you use working standards as gages to check measuring equipment throughout production and those standards are traceable, then you are doing fine. The processes you use to verify the tools and any in-process measuring practices should be documented in Work Instructions or even with the use of photographs or flow charts.

In the second part of your question, you ask if there is a difference between 9001 and TS 16949. I reference section 7.6.1 of TS 16949. Here it is put straight forward:

7.6.1 Measurement System Analysis

Conduct statistical studies to analyze variation present in the results of each type of MMD that is referenced in the Control Plan.

Use analytical methods & acceptance criteria that:

Conform to methods and criteria in customer reference (MSA) manuals Or use other methods, if approved by the customer

This is an automotive sector specific QMS standard. Herein it is necessary to consider safety and liability in everything you do. So, Gage R&R’s are a common practice. Nonetheless, the necessity for these is dictated by individual processes. Some may need them, some may not.

So, if an instrument is listed on YOUR control plan, GRR’s will become a requirement based on all the criteria I’ve noted above. A gage which has proven stability is most often safe from that requirement under 9001 but TS16949 has more extensive requirements.

Bud Salsbury, CQT, CQI

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AS9100C

Airplane, aerospace, AS9100

Question:

Question: AS9100C, which is an expansion of the ISO 9001:2008, states that a “process” based system is being promoted as is shown in 0.2 of the Introduction. Why are 3rd party auditors being required to use the AS9101 Quality Management Systems Audit Requirements for Aviation, Space and Defense Organizations checklists for their audits? These check lists are not “process” based and go back to the old procedure systems of the 1994 standard.

Each of our core processes consists of a flow chart of the process, process turtle and PEAR. If you were doing a true process audit you would take these documents and perform the audit and not limit the auditor to being “boxed in” by a check list. If the QMS has been developed correctly the process approach audit will allow you to cross other processes when being performed.

Response:

Thanks for the question. The IAQG AS9101 team does firmly believe in promoting the process approach which you will see reflected with the next AS9101 revision. I agree that auditors should follow the process while performing all auditing (including 3rd party audits), yet it is also important to ensure that all the AS9100 requirements are satisfied. That is why AS9100 auditors are trained to audit the process and then complete the Objective Evidence Record to ensure all AS9100 requirements are fulfilled.

Thanks,
Buddy Cressionnie
Americas 9100 Lead

For more on this topic, please visit ASQ’s website.

SIPOC

ISO 13485, medical devices, medical device manufacturing

Question:

I’m working on a green belt certification and I have a question about SIPOC. What would be the examples of inputs for hospital test facility? The supplier is physician and patient is the customer?

Response:

Hello,

Here’s an approach to consider:

Supplier=doctor

Input= blood sample, urine sample, sample swab

Process =DNA, microbiology, HVLC

Output =test results

Customer =patient

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Use of Correction Fluid to Modify ISO 9001 QMS Documents

ISO documentation practices, requirements

Q: During a recent audit, I discovered that my supplier was using correction fluid and scrubbing out the training records of its employees with no control over the documents. I said that would be a major finding, but they state that there is nothing in ISO/ANSI/ASQ 9001:2008 Quality management systems–Requirements specifically telling them that they can’t correct records on the fly without any control. Can you clarify this practice for me? I can’t find anything definitive in the standard.

A: This is an interesting question. Sometimes, people complicate standards rather than recognize them for the friendly guides they can be. It is true, as written in clause 6.2.2 of ISO 9001:2008, that records for education, training, skills and experience need to be maintained per clause 4.2.2. However, the standard does not designate a specific process for this.

Clause 4.2.4 expresses a requirement to establish a documented procedure, and also states that the records should be legible. While the practice of using correction fluid or scrubbing out training records is probably not the best and most professional way of handling things, it’s not a cause for a finding of nonconformance.

Records which have a direct affect on customer products would definitely need better controls. However, I think in this case, you might find it wise to work with the supplier to find a better way of recording employee training. The records must remain legible, readily identifiable and retrievable. If that is what they are doing and product quality is not affected, there should be no major finding. A recommendation for continual improvement would be appropriate.

I hope this helps.

Bud Salsbury
ASQ Senior Member, CQT, CQI

Z1.4: Selecting the Sample Size

Pharmaceutical sampling

Q: I work for a pharmaceutical company that manufactures soft gel capsules. What is the proper way to select a sample size when using ANSI/ASQ Z1.4-2008: Sampling Procedures and Tables for Inspection by Attributes?

I’ll further illustrate my question with an example. If one were to have a batch size of 20,000 units, according to General Inspection Level II, Normal, the corresponding letter code is “M.” In the master table for Acceptable Quality Levels (AQLs), the sample size would be 315 units. If my AQL is 0.010 (with an acceptance/rejection number of 0/1 based on the table), does my sample size change to 1250 units? Or does it remain at 315 units?

Your assistance is greatly appreciated.

A: The simple answer is 1250, not 315 suggested for sample size letter M. General Inspection Level II, Normal, shows that for a lot size of 20,000, a sample size code level of M corresponds to a sample size of 315. For an AQL of 0.01, the arrow points to a sample size of 1250 (sample size letter code Q) to have the required AQL of 0.01.

The calculation of AQL is not dependent on lot size. In other words, a sample size of 315 gives a minimum AQL of 0.04, so a larger sample is required to estimate an AQL of 0.01.

Q2: Could you please add another layer to your response? The reason I’m seeking additional clarification is that the first step in determining the sample size is to find the letter code and the corresponding sample size. To me, it feels like the first step should be to determine the AQL.

A2: Let me expand with a more technical explanation. Attribute sampling is based on the hypergeometric distribution and is estimated using the binomial distribution (which assumes an infinite population size).

The basic formula for the binomial is:

AQL and LQ for a given sample size (n) and defects allowed (x):

If n=30, x=0; AQL=0.17%; LQ=7.4%:

If you are using Z1.4, your sample size is selected based on your lot size. Then, you would pick the AQL you need based on the risk you are willing to take for the process average of percent defective. If you decide to not use Z1.4, but instead use the binomial directly, then you are correct that you would decide on the AQL and lot tolerance proportion defective (LTPD) first, then calculate a sample size for c=0, c=1, c=2, and etc.

Steven Walfish
Secretary, U.S. TAG to ISO/TC 69
ASQ CQE
Principal Statistician, BD
http://statisticaloutsourcingservices.com

Related Content:

Acceptance Sampling With Rectification When Inspection Errors Are Present, Journal of Quality Technology

Zero Defect Sampling, World Conference on Quality and Improvement, open access

Explore ASQ’s website for more case studies, articles, benchmarking reports, and other content about zero defect sampling.