Since launching my Root Cause Analysis class just over 5 years ago, I count myself remarkably fortunate to have been a part of the learning journeys of the 14,000+ students who have taken it. And a welcomed part of teaching courses online is fielding questions that come from students. In addition to clarifying for them various technical points of the course, I also get a “behind the curtains” look at the general training gaps in the quality profession. Afterall, that one student’s question may be in lingering in the minds of countless other quality professionals as well.
So in this three-part article series, I will highlight some of the best “real life” questions (occasionally edited for clarity) students of my Root Cause Analysis have asked, along with my responses, in the hopes that you gain some insight from one or two of them as well.
Hello Ray,
Based on your experience, what is the best way to get people committed to answer the CARs. I find that the most difficult part for the CAR issuers (internal auditors) is to get people involved to respect the timing to answer each of the CAR phases. There is an internal procedure that defines the time for each phase but most of the time CARs are OD.
Hello Rosser … You’re asking a question that many quality professionals have.
In these cases, I think auditors have two major responsibilities:
1. Setting and communicating reasonable timeframes that allow others to provide thorough responses, but short enough to emphasize the importance of effectively closing these CAR’s.
2. Communicating to the whole organization, including top management, the importance of closing these CARs on a timely basis. This is not just important to prevent a recurrence of the same defects, but also to remain in compliance with your quality system standard.
Once these jobs are done, it is really the responsibility of top management to make sure their organizations are complying with the established standards.
Often engineers and managers will claim that they are too busy. But that is not an excuse for failing to complete these. This is where the appropriate level of management needs to provide to resources to assure these CARs are closed.
I hope that helps. Thanks so much for reaching out.
Hi Ray,
I have a question on non-conformances during sampling.
So generally, we select samples to inspect whether that lot is good or bad. And if the defective parts found in the sample is within AQL, then we pass the lot. So how does non-conformance play out here since we already passed the lot?
Does it apply only to that lot which did not pass the sampling stage? Can you please elaborate on these? I am having a little bit of confusion.
Hello Rajeev,
Sample inspection is a method for reasonably assuring that the lots your producing have been made to the customer requirements. And when developing a sampling plan, the quality engineer is balancing the probability of finding a defective part, should it exist in a particular lot, against the cost of that sampling process. In other words, as the sample size increases, so does the probability of finding a bad part AND the cost of performing that sample inspection.
So typically, when a defective part is found in a sample, the entire lot is segregated for further inspection, usually 100% inspection. If no defective parts are found in the sample pulled, then the lot is approved without further inspection.
And this type of sampling process can happen at various stages throughout the process, though it’s most often applied when the product is completed.
Hope that helps explain the typical acceptance sampling process.
Hello Ray,
I liked the matrix of “Ease of implementation & Impact” that you presented to select the activities that will be implemented. I would like to know if there is an accurate way to evaluate the impact of the corrective actions before implementing them. Are there any recommendations to follow to determine whether a corrective action will have a big impact?
Thank you for your help!
Hello Josue,
So good hearing from you and I’m glad you liked my Impact matrix. It has served as a framework in my thinking for many years.
The true effectiveness of a corrective action can only be estimated using assumptions and educated guesses. However, the potential impact of corrective activities can be more accurately estimated because you should know the cost of the problem or defect you’re chasing.
For instance, if you are looking at a year’s worth of warranty claims and you categorize and rank their costs using pareto analysis, you will know your highest costs claim categories.
From there, you dig into the root causes of the highest-ranking defect. You may find 5 or 6 root causes to that top defect. At that point, you’re only guessing what percentage of the problem can be assigned to each root cause. But as you start eliminating the root causes, you should be able to see the new costs for that warranty claim category starting to fall.
I know this isn’t an exact answer, but at least part of the answer is understanding your true quality costs and using pareto analysis as a guideline for tackling them.
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