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| articles:whac-a-mole [2023/03/16 18:57] – [What about "Zero Defects"?] rrandall | articles:whac-a-mole [2024/02/05 21:17] (current) – [The "Human Factors" in Cause & Effect Analysis] rrandall |
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| | **Assignable Cause** | unusual / abnormal,\\ not previously observed,\\ non-quantifiable variation | | | **Assignable Cause** | unusual / abnormal,\\ not previously observed,\\ non-quantifiable variation | |
| </WRAP> | </WRAP> |
| The staff is well trained and rarely make these mistakes. If one were to initiate a "corrective action" to address this situation, it would quickly prove futile because there is __NO "assignable" root cause__ to be eliminated. This type of error is a normal, random (common cause) variation in the restaurant's process due to the volume of silverware that is washed, sorted, and manually rolled into napkins by the staff. | The staff is well trained and rarely make these mistakes. If one were to initiate a "corrective action" to address this situation, it would quickly prove futile because there is __NO "assignable" cause__ to be eliminated. This type of error is a normal, random (common cause) variation in the restaurant's process due to the volume of silverware that is washed, sorted, and manually rolled into napkins by the staff. |
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| However, one night you arrive and order dinner only to find that the food takes much longer than normal to arrive at your table has been over-cooked and is cold. You complain to the server who apologizes explaining that their chef is unexpectedly absent tonight due to an illness. And that this was terrible timing because his Assistant chef is traveling on vacation. Consequently, a replacement chef, who is unfamiliar with both their kitchen and menu, had to be brought in to fill this temporary need. | However, one night you arrive and order dinner only to find that the food takes much longer than normal to arrive at your table has been over-cooked and is cold. You complain to the server who apologizes explaining that their chef is unexpectedly absent tonight due to an illness. And that this was terrible timing because his Assistant chef is traveling on vacation. Consequently, a replacement chef, who is unfamiliar with both their kitchen and menu, had to be brought in to fill this temporary need. |
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| Unlike the silverware issue, this is an unusual/abnormal, situation that has not previously occurred. Therefore, this would be a “special cause” variation in their process __with an "assignable" root cause__. Special causes produce systematic effects/errors in a process. | Unlike the silverware issue, this is an unusual/abnormal, situation that has not previously occurred. Therefore, this would be a “special cause” variation in their process __with an "assignable" cause__. Special causes produce systematic effects/errors in a process. |
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| The [[https://support.minitab.com/en-us/minitab/18/help-and-how-to/quality-and-process-improvement/control-charts/supporting-topics/basics/using-control-charts-to-detect-variation-in-a-process/|Minitab® 18 Support web site]] offers "**Examples of common-cause and special-cause variation**" in a table (provided below with a few minor improvements). | The [[https://support.minitab.com/en-us/minitab/18/help-and-how-to/quality-and-process-improvement/control-charts/supporting-topics/basics/using-control-charts-to-detect-variation-in-a-process/|Minitab® 18 Support web site]] offers "**Examples of common-cause and special-cause variation**" in a table (provided below with a few minor improvements). |
| ==== Reactive Process Improvement ==== | ==== Reactive Process Improvement ==== |
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| In order to properly implement a "corrective action", there must be an assignable "root cause". And in order for there to be an assignable "root cause", the nonconforming condition must be the result of a "special cause" variation (i.e., an “unnatural pattern” in the process, which is unusual, not previously observed, non-quantifiable variation in the process). | In order to properly implement a "corrective action", there must be an "assignable cause". And in order for there to be an "assignable cause", the nonconforming condition must be the result of a "special cause" variation (i.e., an “unnatural pattern” in the process, which is unusual, not previously observed, non-quantifiable variation in the process). |
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| Consequently, because "special causes" produce systematic effects/errors in a process, properly implemented "corrective actions" are __reactive__ process improvements... refining an existing process. | Consequently, because "special causes" produce systematic effects/errors in a process, properly implemented "corrective actions" are __reactive__ process improvements... refining an existing process. |
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| ===== The "Human Factors" in Cause & Effect Analysis ===== | ===== The "Human Factors" in Cause & Effect Analysis ===== |
| While we're on the topic of "Human Errors", these are very much prevalent in the Cause & Effect Analysis process. | While we're on the topic of "Human Errors", these are very much prevalent in the Cause & Effect Chain Analysis process. |
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| First, the individual(s) performing the Cause & Effect Analysis have their own bias for what the "Root Cause" should be. Like it or not, a "Blame Game" often occurs during this process. No individual or manager wants to be the target of that "negative" perception. | First, the individual(s) performing the Cause & Effect Chain Analysis have their own bias for what the "cause(s)" should be. Like it or not, a "Blame Game" often occurs during this process. No individual or manager wants to be the target of that "negative" perception. So "finger pointing" often ensues. |
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| Another important "Human Factor" is that humans have evolved to "think" in a linear fashion. Consequently, people have difficulty making sense of non-linear events that have branches and/or parallel causes/effects. Read any Corrective Action Report and you will see a linear story detailing the events in a sequence... omitting any parallel causes. | Another important "Human Factor" is that humans have evolved to "think" in a linear fashion. Consequently, people have difficulty making sense of non-linear events that have branches and/or parallel causes/effects. Read any Corrective Action Report and you will see a linear story detailing the events in a sequence... omitting any parallel causes/effects. |
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| Sadly, most Quality Professionals have not been taught that every event must have at least one condition and one action. Similarly, most Quality Professionals have also not been taught that upon identifying a "Cause - Effect" relationship, the "Effect" now becomes the "Cause" for the next step in the analysis. In other words, whether something is a "Cause" or "Effect" depends upon the analyst's perspective. | Sadly, most Quality Professionals have not been taught that every event must have at least one condition and one action (i.e., "[[https://www.amazon.com/Apollo-Root-Cause-Analysis-Thinking/dp/1883677114|Apollo Root Cause Analysis]]"). Similarly, most Quality Professionals have also not been taught that upon identifying a "Cause - Effect" relationship, the "Effect" now becomes the "Cause" for the next step in the analysis. In other words, whether something is a "Cause" or "Effect" depends upon the analyst's perspective. |
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| Also, the simple "5 Whys" method only goes to the point of the analyst's "ignorance"... NOT the "Root Cause". In other words, the analyst asks "Why?" until he cannot answer the question. Out of ideas, he assumes that is the "Root Cause"... when in reality, the analyst(s) has merely reached their "Point of Ignorance". While the analyst could continue the analysis by obtaining participation from one or more people (Subject Matter Experts) who can answer that question, they too would eventually encounter their "Point of Ignorance". | Also, the simple "5 Whys" method only goes to the point of the analyst's "ignorance"... NOT the mythical "Root Cause". In other words, the analyst asks "Why?" until he cannot answer the question. Out of ideas, he assumes that is the "Root Cause"... when in reality, the analyst(s) has merely reached their "Point of Ignorance". While the analyst could continue the analysis by obtaining participation from one or more people (Subject Matter Experts) who can answer that question, they too would eventually encounter their "Point of Ignorance". |
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| Consequently, one could easily argue that identifying the true "root cause" of any event is impossible. | Consequently, the "5 Whys" method leads to untrained analysts ignoring multiple links in the cause-and-effect chain... many of which would prevent the recurrence of the nonconformity. |
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| ===== Conclusion ===== | ===== Conclusion ===== |
| </WRAP> | </WRAP> |
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| IF a nonconformity is due to a “Common Cause” variation, then "controls" can be put in place to "__mitigate__" the risk of the nonconformity recurring. However, IF a nonconformity is due to an "Assignable Cause" variation, then the process can be changed to "__eliminate__" the cause of the nonconformity recurring (i.e., reducing the probability OR impact of a risk to zero). | IF a nonconformity is due to a “Common Cause” variation, then "controls" can be put in place to "__mitigate__" the risk of the nonconformity recurring. However, IF a nonconformity is due to an "Assignable Cause" variation, then the process could possibly be changed to "__eliminate__" the cause of the nonconformity recurring (i.e., reducing the probability OR impact of a risk to zero). |
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| Upon completing a PFMEA ("Process Failure Mode and Effects Analysis"), one quickly realizes just how few "true" corrective actions are actually possible. And that by shifting the mindset to "risk management", rather than being obsessed with "risk elimination" (aka "Corrective Action"), significant quality improvements can finally be realized. | Upon completing an FMEA/FMECA or Risk Register, one quickly realizes just how few "true" corrective actions are actually possible. And that by shifting the mindset to "risk management", rather than being obsessed with "risk elimination" (aka "Corrective Action"), significant quality improvements can finally be realized. |
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