Using the 10:1 Ratio Rule and the 4:1 Ratio Rule

Q: Can you explain when I should be using  the 10:1 ratio rule and the 4:1 ratio rule within my calibration lab? We calibrate standards as well as manufacturing gages.

A: First, I will use the right nomenclature. What the user means is 10:1 and 4:1 Test Accuracy Ratio (TAR). That is, one uses standards 4 or 10 times as accurate as the Unit Under Test (UUT) to calibrate it with.

Unfortunately, the answer to the user’s question is NEVER if we were to use newer metrologically accepted practices.

The TAR is replaced by Test Uncertainty Ratio (TUR).  The ANSI/NCSLI Z540.3:2006 definition of TUR is:

“The ratio of the span of the tolerance of a measurement quantity subject to calibration, to twice the 95% expanded uncertainty of the measurement process used for calibration.”

*NOTE: This applies to two-sided tolerances.

The TUR is represented as a mathematical equation below:

Test Uncertainty Ratio (TUR) represented as an equation

Because of advances in technology, one can purchase highly precise and accurate instrumentation at the end user level, it gets challenging to find standards 4 or 10 times as precise with which to calibrate it and maintain metrological traceability at the same time (definition per ISO Guide 99:2007, Property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty).

Proper measurement uncertainty analysis of the UUT (including standards used with its uncertainty) identifies all the errors associated with the measurement process and ensures confidence that calibration is within the specification desired by the end user.

ISO/IEC 17025-2005: General requirements for the competence of testing and calibration laboratories, clause 5.10.4.2, third paragraph, also states that “When statements of compliance are made, the uncertainty of measurement shall be taken into account.”

This would also ensure confidence in the calibration employing the metrological and statistical practices recommended.

The other rule of thumb not to be confused in this discussion is to measure/calibrate with the right resolution. In the ASQ Quality Progress March 2011 Measure for Measure column, I wrote more on resolution with respect to specification and measurement uncertainty. The general rule of the thumb is if you want to measure/calibrate a 2-decimal place resolution device, you need at least 3-decimal place or higher resolution device.

This is a very good question posed and it is also unfortunately the most misunderstood practice among a lot of folks performing calibration.

Dilip A Shah
ASQ CQE, CQA, CCT
President, E = mc3 Solutions
Chair, ASQ Measurement Quality Division (2012-2013)
Secretary and Member of the A2LA Board of Directors (2006-2014)
Medina, Ohio
emc3solutions.com

Related Content: 

Measure for Measure: Avoiding Calibration Overkill, Quality Progress

Evolution of Measurement Acceptance Risk Decisions, World Conference on Quality and Improvement

Measure for Measure: Calculating Uncertainty, Quality Progress

Is C=0 in Z1.4?

Chart, graph, sampling, plan, calculation, z1.4

Q: I have ANSI/ASQ Z1.4-2008 Sampling Procedures and Tables for Inspection by Attributes. I looked through it rapidly, and I still can’t find the C=0 plan directly, so I am a little confused. I thought C=0 is included in Z1.4. Is the C=0 plan spirit/concept contained in Z1.4 or does C=0 need to be calculated from the several tables in Z1.4? (if yes, which tables?).

A: Z1.4:2008 is a general sampling plan for attributes.  It is tabled by AQL with varying accept reject numbers.  The standard gives a framework for attribute inspection plans. Though Z1.4 does have some plans where C=0, they are NOT optimal to minimize the Type II error. For C=0 plans specifically, I would recommend purchasing Zero Acceptance Number Sampling Plans, Fifth Edition.  The value of the Z1.4 standard is the switching rules used for incoming inspection.

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

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

Measurement Tolerances and Techniques

ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratoriesQ: I am looking for some information regarding blueprint tolerances and measurement tools used to measure certain features.

For example, can the same type of tolerance be applied over the length of 450 mm as it could be for a distance of 3 mm?  Is there additional measurement error or gage error that needs to be applied for longer distances?  If one uses a 1” micrometer for measuring a feature, does it make a difference in the measurement error by using the top end of the instrument versus using it to measure just very small features?

A: Thank you for your questions about measurement tolerances. First of all, since your questions were multi-layered, my answers will be as well. Nonetheless, I think I should be able to help you.

As for using the same type of tolerance for a dimension of 450 mm and a dimension of 3 mm, there is more than one answer. We’re talking about 17.7165 inches vs. .118 inches. The 3 F’s must first be considered.  That is Form, Fit, and Function.  In other words, where will this product be used?  If this will be for a medical product or for anything whatsoever where safety is a factor, the design engineer will most likely use a tighter tolerance. So both dimensions could be ± .001 or a more liberal ± .010.  The difference between the two sizes would just change the way they are manufactured.  For example: a 17.717 inch product with a tolerance of ± .030 could probably be rough machined or even made on a burn table.  If the size or location of the smaller dimension is critical, you would machine it with appropriate equipment and hold a tighter tolerance.  OK, enough Manufacturing 101 lingo.

With regard to measurement error, larger/longer dimensions can introduce the possibility of increased measurement error. However, if a “qualified” and experienced individual is doing the measurement, that should not be a major factor.  The same basic skills and standards would apply. The type of measurement equipment can make a difference.  In other words; if you use a Dial Caliper, you can probably rely on it to be accurate within .001-.002 inches.  If you use a 0-1 inch micrometer, you should be able to trust it’s accuracy within .0001 inch.

A qualified metrologist and/or a quality technician would know to check a micrometer at numerous points over its measuring range.  Measurement error should not increase significantly from one end to the other.  If it does, there is something wrong with the calibration or with the tool itself.

I know the above can be perceived as general answers, but I am confident you will see the specifics there as well.

Bud Salsbury
ASQ Senior Member, CQT, CQI

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

ISO 14001 4.3.1 Environmental Aspects; Clarification of Intent

ISO 14004, Environmental Management System, EMS

Q: Based on Section 4.3.1 of ISO 14001-2004: Environmental management systems – Requirements with guidance for use, would an organization control, or be expected to influence, environmental aspects in the following situations:

  • Would an organization’s headquarters (or corporate office) control, or be expected to influence, the environmental aspects of its operating facilities?
  • Would an organization control, or be expected to influence, the environmental aspects of its suppliers, including contractors?
  • Would a regulatory agency control, or be expected to influence, the environmental aspects of other organizations subject to its regulatory requirements?

Clarification of Intent:

A: Clause 4.3.1 of ISO 14001:2004 requires an organization to identify the environmental aspects of its activities, products and services within the defined scope of its environmental management system (EMS) “that it can control and those that it can influence.”  This differs from the 1996 standard which used the phrase “that it can control and over which it can be expected to have an influence.”

The revised language removes one ambiguity in the 1996 version – some users incorrectly interpreted this phrase to imply that views of someone outside the organization must be considered when determining the environmental aspects the organization might influence. The intent of the new phrase in Clause 4.3.1 is to make it clear that the organization makes that determination.

Furthermore, as in the 1996 standard, the organization is obligated to identify environmental aspects only for those activities, products and services that are within its EMS scope, which again is decided by the organization (see Clause 4.1). Of these environmental aspects, the organization must decide which it can control and which are not within its control.  For those of its environmental aspects that it cannot control, the organization must decide if it can exercise influence over them

The Standard does not define criteria that an organization must use to determine its control of or influence over environmental aspects.  It is up to the organization to make that determination, on a case by case basis, considering its own unique factors, such as its governance structure, legal or contractual authority, its policies, local or regional issues, its obligations and responsibilities to interested parties, technological issues and implications on its own environmental performance. What might be appropriate for one organization might not be appropriate for others. It is important to note that it is possible for two different organizations or two different organizational units to control or influence the “same” environmental aspect.

In summary, an organization is only responsible for managing its own environmental aspects (those arising from activities, products, and services within its EMS scope) and only those aspects which it can control or which it can influence.

Regarding the three situations posed in the question:

1) Determining “control and influence” within a corporation or other hierarchical organization.   For purposes of identifying environmental aspects, the scope of the EMS is the key.  It delineates the activities, products, and services from which environmental aspects might arise and for which the organization needs to consider its control or influence.

If the EMS scope is restricted to corporate headquarters, the issue of control or influence pertains to the environmental aspects arising from headquarters’ activities, products and services.  It may be that some environmental aspects are not within corporate headquarters control, but instead are controlled by an operating facility.  In this case, corporate headquarters must consider whether it can influence those aspects that are within its scope and yet controlled by the operating facility.

If the EMS scope is restricted to one operating facility, the issue of control or influence pertains to that operating facility.  It may determine that some environmental aspects are not within the operating facility’s control, i.e., certain aspects may be controlled by another operating unit (such as headquarters or an engineering department).  The operating facility must consider whether it can influence those aspects that are within its EMS scope and yet controlled by another unit.

If the EMS scope includes both headquarters and the operating facilities, both headquarters and operating facilities need to consider their collective control or influence over the aspects within the scope of the EMS.

2)  Determining “control and influence” with regard to contractors and suppliers.   An organization is not responsible for the environmental aspects of its contractors or suppliers; it is responsible only for its own environmental aspects.   An organization may have environmental aspects associated with activities within its own EMS scope which are performed by contractors, or environmental aspects arising from materials or services purchased from suppliers.  For such aspects, the organization must consider what control it might have, e.g. through contracts, and what influence it might have, e.g. through purchasing power.

3) Determining “control and influence” for a regulatory agency.   When a regulatory agency identifies environmental aspects associated with its activities, products, and services, it must consider the same issues as other organizations; that is, it must determine the extent of control or influence it has over the identified aspects.  It is clear that such an agency may influence or even be perceived to control some environmental aspects associated with organizations that it regulates.  The important point is defining the regulatory agency’s environmental aspects that arise from the activities (e.g., setting water quality standards), products (e.g., discharge permits), and services (e.g., inspection) within its EMS scope.  Deciding which aspects are under the agency’s control or influence follows the same logic as for other organizations.

U.S. Technical Advisory Group (TAG) 207 Task Group on Interpretations

– – – – – – – – – – –

What are clarifications of intent?

The ISO 14001:2004 standard on environmental management systems has been negotiated over a period of years, with language carefully chosen to reflect delicate compromises and flexibility in their use and application.

Recognizing that questions of intent may arise from time to time in various settings, the U.S. TAG responds to questions regarding clarification of the ISO 14001 requirements. These responses reflect U.S. SubTAG 1’s understanding of the requirements as intended during its drafting. Responses are prepared by the SubTAG 1 Clarification of Intent Drafting Group, which consists of the Administrator, the U.S. SubTAG 1 Working Group experts and others who participated in the drafting of the ISO 14001 and 14004 standards. Responses are developed based on the group’s consensus understanding of the intent of the SC1 Working Group members who drafted the standard.

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

Six Sigma Green Belt Projects

Data review, data analysis, data migration

Q: I teach a course called “Statistical Methods of Six Sigma” at an engineering college. I’m preparing students to take the ASQ Certified Six Sigma Green Belt exam if they are interested (it is not a mandatory requirement of my class).

Here’s my question — most of my students already have jobs lined up after graduation. Some of them are going to places where Six Sigma programs are already fully established. I do have one particular student who is expected to implement a Six Sigma program at the company that she is going to. It’s a small company, and they don’t already have a Six Sigma program in place.

If she passes the ASQ Green Belt exam and receives her Six Sigma Green Belt Certification, how does she go about getting a project approved if she’s working for a company that doesn’t already have existing Belts?

A: To ask a Green Belt to implement a Six Sigma program is not only ambitious, but also somewhat risky.  Green Belts have the least amount of experience in Six Sigma. Regardless, what this person should be doing is look at the company and decide what a good first project would be with an executive mentor.  The candidate should be looking at something that is important to the company and has impact to the business.  It should be something that requires some work and is not obvious to just anyone looking at the project.

Q: I think the expert more accurately posed what my real question is: how does a new grad working for a company that doesn’t currently have a Six Sigma Black Belt program find an executive mentor to approve or qualify her project?

I agree that she will need a Black Belt, but who will/can certify her project if there is not an existing Black Belt or Master Black Belt at her place of work?  (It is a small consulting firm for medical hospitals).

A: I recommend that she approach her local ASQ Section and inquire about mentors.

Jim Bossert
SVP Process Design Manger, Process Optimization
Bank of America
ASQ Fellow, CQE, CQA, CMQ/OE, CSSBB, CMBB
Fort Worth, TX

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

ISO 17025 Certified Facility

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

Q: We have a specification that states test reports shall be from an facility certified to ISO 9001:2008 Quality management systems–Requirements. Our test reports are from a facility certified to ISO/IEC 17025-2005: General requirements for the competence of testing and calibration laboratories.

Isn’t ISO 17025:2005 under the ISO 9001:2008 umbrella?

A: Your interpretation is, indeed, correct. Actually, for a testing lab, accreditation to ISO/IEC 17025 is superior to registration to ISO 9001! As you know, your accreditation agency actually observed your personnel performing tests. They had to demonstrate competency. This was in addition to the verification that you had a working management system in place (that’s why they call it accreditation and not registration. We won’t even get into the misuse of the word certification).

To make sure your customer gets the assurance they want, I recommend you contact your accreditation agency. Ask them for a letter that states this equivalency. That will probably blow your customer away – or at least amaze them! Unless you can show the text you provided to ASQ was from one of the ISO or ANSI standards-writing committees, as an official interpretation, it probably holds little weight.

Your customer is right to monitor your performance this way. Recent food safety issues, prominent in the news, have a common element to them — insufficient attention to supplier performance. Expect to see more of this as the manufacturers and distributors pay more attention to their supply chain. I expect you are or will be doing the same for your critical sub-suppliers. Remember too, there are many ways to monitor supplier performance. Registration/accreditation is one of the ways.

Dennis Arter
ASQ Fellow
The Audit Guy
Columbia Audit Resources
Kennewick, WA
http://auditguy.net

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

Z1.9 Sigma for Variability Known Method

Audit, audit by exception

Q: I have a question about  Z1.9-2008: Sampling Procedures and Tables for Inspection by Variables for Percent Nonconforming. I have seen there is a “Variability Known” method. However I don’t know how to get a Sigma, so I don’t know how to use this method. Could you please share how to get a Sigma?

A: To get a Sigma to use for the Variability Known method is to have data that has been collected over a period of time and calculate the standard deviation. The rule here is at least six months of data with at least 50 data points.  Depending on the process, if the data has been collected and there is over 1000 data points, the time limitation goes away since you have an extremely large data set to work with.

Q: During the 6 months, the process should be under control, right? And data should be normal distribution, right? Is there any process control needed? And how do I maintain this process and Sigma?

A: Yes, there is the assumption that the process is normally distributed and is stable.  That means some type of process control is being used.  Ideally this would be an X-bar and r or an X-bar and S chart. If an out of control situation occurs and you can bring the process back into control, then you are ok.

Q: Could you tell me the meaning of “data point”? As you know, during the 6 months, we will get lots of batches. For each batch, we will have a certificate of analysis (COA), and many data. I am not sure how do you combine data for different batches. How do you calculate this?

A: Data point, in the most simple format, could be the statistics associated with a batch or a mean and standard deviation/range. Each batch gives you a new set of data points. You can combine the time based data in a couple of different ways:

1. You can take each batch and use the means and plot them on an X-bar and R or an X-bar and S-chart.
2. You can take the raw data and combine it into one large distribution.

The preferred way is the control chart approach since you will know if the process is stable since it is already plotted.

Jim Bossert
SVP Process Design Manger, Process Optimization
Bank of America
ASQ Fellow, CQE, CQA, CMQ/OE, CSSBB, CMBB
Fort Worth, TX

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

AS9100 Production Rough Card

Aerospace, AS9100, Requirements, Standard

Question

According to our customer requirement, our quality inspectors are signing each step in production rough card in the following way: they apply their personal stamp (which includes their first and last name and personal number), add a manual signature and date. I tried to convince our customer to give us permission to eliminate the manual signature (as the personal stamp and date are enough), but he doesn’t agree with me.

Is there any official standard for this procedure? I was not able to find any special requirement for this in AS9100 Rev. C  – Requirements for Aviation, Space and Defense Organizations.

Answer

The AS9100 standard does not dictate any specific method of recording that a production step (clause 7.5.1) or verification step (clause 8.2.4) is complete. AS9100 does require the organization to comply with customer requirements. So this is a requirement which you need to discuss with your customer.

Buddy Cressionnie
International Aerospace Quality Group Americas AS9100 Lead
Voting member of the U.S. TAG to ISO/TC 176
Southlake, TX

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

Z1.4 or Z1.9 Sampling Plan for IT Tickets

Data review, data analysis, data migration

Q: I need to purchase a sampling standard. However I notice there are a few options for sampling plans, such as attributes vs. variables.  I am not sure which one will best fit my needs.  I need help in determining this.

I need to determine what the best sample size would be for recurring IT operations.  For example:  If my server team closes 500 tickets a month and I want to pick a sample size to review for quality purposes, what is the best chart to use to determine what the industry standards say are the recommended sample size?  My understanding is there is a light, normal and heavy chart that can be offered.

Please help.  Thanks!

A: The answer is “it depends.”  What it depends on what is she reviewing for quality purposes?  If the inspection is for either “good quality” or “poor quality,” then Z1.4-2008: Sampling Procedures and Tables for Inspection by Attributes, would be appropriate.  If she is measuring something, “time to close,” for example, then Z1.9-2008: Sampling Procedures and Tables for Inspection by Variables for Percent Nonconforming, might be appropriate, although Z1.9 is really only good if the data are normally distributed, which waiting times are generally not.

With more information, I could provide a more definitive answer.

Q: Our intention right now, is to evaluate tickets closed  (or work processed, which could be in other facets other than tickets, may be items logged in a log sheet to check service statuses, etc) to determine if the quality of work performed meets our quality standards.  We are determining what “quality” means to us.  For example:  We want to look at tickets closed to determine if the ticket was escalated properly from our tier 1 to tier 2 team AND if the work log of that ticket had the correct data and correct amount of data documented.  Meaning a tech didn’t just say “resolved user issue,” but rather they documented more relevant data about what they did to resolve the issue.  All of the work performed is service delivery in an operations environment, so the evaluations will be performed on the quality of following our processes and the quality of our resources.  We have an amount of tickets closed per month that vary, slightly up or slightly down.  I want to look at a table to determine what our sample size should be.

However, in addition to the above, I am very interested in learning the other plan too because we do have Service Level Objectives (SLO’s and SLA’s) in this environment (example: time to close, first call resolution, call abandonment rate, etc) If I can understand that other table and how to use it, both may be valuable and I may purchase both.

I didn’t understand the comment that “Z1.9 is really only good if the data are normally distributed, which waiting times are generally not.”  What does normally distributed mean?  I would like that explained.
Can your expert answer and provide information on both sampling plans for me?

Thanks again and I look forward to the response.

A: Normally distributed means that the data follow a bell-shaped curve with the most frequency values falling around some average and tailing off in frequency both above and below that average.  Many processes in real life follow the normal distribution.  Time to close is an exception.  It is more likely to follow the exponential distribution, which means that there will be lots of tickets closed at shorter durations, with some tailing out very far into longer durations.  Also a ticket can’t be closed at less than 0 duration.  The normal distribution extends, in theory, to +/- infinity.  Rates (percentages, I’m assuming) can often be approximated using the normal distribution as long as they aren’t too near 0% or 100%.  If they are near the edges a square root transformation often help to make the data more approximately normal.

Most of the quality characteristics you described are of the pass-fail variety which implies Z1.4 would be appropriate.

I strongly recommend that you take a course and/or read a book on statistical process control or acceptance sampling before attempting this. 

Brenda Bishop
US Liaison to TC 69/WG3
CQE,CQA,CMQ/OE,CRE,SSBB,CQIA
Belleville, Illinois

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

Framework to Integrate ISO Standards and Non-ISO Standards

Reviewing confidential files, training records, human resources files

Q: I have a few questions about integrating standards for one of the experts:

1) Will registrars (in addition to BSI, who wrote it) accept a documented quality management system organized around the framework suggested in PAS 99:2006 – Specification of common management system requirements as a framework for integration, given there is adequate audit evidence that the requirements of both of the integrated standards have been addressed and have been implemented?

2) Is PAS 99 only for ISO-related standards, e.g.,  ISO 9001:2008 Quality management systems–Requirements and  ISO 14001-2004: Environmental management systems – Requirements with guidance for use, or can other combinations be made – e.g., ISO 9001 and American Institute of Steel Construction-Bridge and Highway AISCQC028?

AISCQC028 is not an ISO or ISO sector-specific standard, although the framework and structure is very similar. The AISC has its own certification body (registrar) and would insist that their auditors conduct a certification audit even though an organization has been previously ISO registered. AISC does not object to an integrated system that integrates/combines ISO 9001 with one of their certification standards as long as AISC certification requirements have been addressed.

The integration of ISO 9001 and 14001 is becoming common place and I’m fairly certain that PAS 99 is an acceptable format in those cases. I’m more interested in other industry standards and requirements not generally considered ISO-related that are being demanded by certain customer segments and integrating them in a system that must also be acceptable to ISO registrars because of other customer segments who are demanding ISO registration by their suppliers.

A: This is an excellent, and timely, question.

More and more organizations are developing integrated management systems based on multiple specification standards – such as ISO 9001, ISO 14001 and OHSAS 18001.   In addition, there are more and more management system standards being developed.  This includes both ISO standards and non-ISO standards – such as OHSAS 18001, Responsible Recycling (R2) and, based on your question, AISCQC028.

It is not even clear how many different management system specification standards there are. What one individual considers a guidance document; someone else insists is a specification standard suitable for certification.

So when you are developing documentation for an integrated management system, how should it be organized?

There are several options:

•    One option is to choose one of the standards as the primary high-level structure – say, ISO 9001:2008 – and address the requirements of the other standards within that structure.

•    PAS 99:2006 offers a different option for a high-level framework for organizing the management system documentation for an integrated management system.  (As you correctly point out in your question, PAS 99 cannot be used as a replacement specification standard for any of the discipline-specific management system standards.)

•    Another option is to establish a high-level structure that makes sense for your organization.

There is no required framework for organizing management system documentation.  You can use whichever overall structure and numbering scheme works for your organization.

ISO has recognized that having different high-level structures for its various management system standards may be problematic for organizations that are implementing integrated management systems that are intended to meet the requirements of multiple specification standards.  As a result, in February 2012, the ISO Technical Management Board (TMB) approved a guide for ISO standard writers that specifies a common structure and definitions to be used for all new and future revisions of ISO management system standards.  This was circulated as ISO Guide 83. This action by ISO highlights the primary issue with using PAS 99:2006.  It is out-of-date.

First, the normative references listed in PAS 99:2006 are not the current versions for some of the standards (notably ISO 9001 and OHSAS 18001).  Second, the high-level structure set out in PAS 99:2006 is not consistent with the common structure recently approved by ISO.

The key to establishing an integrated management is NOT the use of a particular organizing framework or high-level structure.  How you organize your management system documentation needs to fit the needs of your organization – not the desires of a particular registration auditor.

What is important is being able to clearly explain how your management system meets the requirements of each of the specification standards to which you want to become certified.  This requires clearly written documentation that defines the links to the requirements you are addressing within your management system.  It may also require discussion with your registrar and/or the use of reference tables – similar to those set out in the Annexes of ISO 9001, ISO 14001, OHSAS 18001 – and PAS 99:2006.

Thea Dunmire, JD, CIH, CSP
ENLAR Compliance Services, Inc.
Thea’s Blogs:
http://www.OHSAS18001expert.com
http://www.managementsystemexpert.com