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articles:whac-a-mole [2019/04/12 14:18]
rrandall [Proactive Process Improvement]
articles:whac-a-mole [2019/05/29 10:21] (current)
rrandall [Corrective Action... and "Whac-A-Mole"]
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 ====== Corrective Action... and "​Whac-A-Mole"​ ====== ====== Corrective Action... and "​Whac-A-Mole"​ ======
  
-While "​Corrective Action"​ is an essential component for any quality management system, surprisingly few quality professionals have a good understanding of it.+While "​Corrective Action"​ is an essential component for any quality management system, surprisingly few quality professionals have a good understanding of it. This is most often because so many quality professionals lack a basic understanding of "​Common Cause" vs "​Special Cause" variation in a process.
  
-While I realize that the following is a simplistic, "goofy" ​example (itself open to criticism), bear with meLet's assume that on warm summer days, you regularly ride a bicycle along your favorite open bike pathHoweveron one particular day, your front tire hits a small stick at an awkward angle causing you to fall from your bicycle and break your armAfter your arm is healedyou return to that spot where you fell, and sweep that specific area clear of any small sticks that may have fallen, or been blown by the wind, from nearby trees. +These concepts were first described by [[https://​en.wikipedia.org/​wiki/​Walter_A._Shewhart|Walter A. Shewhart]] in his 1931 book, "//Economic control of quality of manufactured produc//t"​. ​And promoted by the [[https://​en.wikipedia.org/​wiki/​Western_Electric|Western Electric Company]] in its 1956 book"//​Introduction ​to Statistical Quality Control handbook//"​ (1 ed.). Laterthese concepts were popularized ​by [[https://​en.wikipedia.org/wiki/W._Edwards_Deming|WEdwards Deming]] in his 1982 book"//​Out ​of the Crisis: Quality, Productivity and Competitive Position//"​. ​Unfortunately,​ there are still many quality professionals who remain oblivious to these concepts!
- +
-Would you consider that to be an effective corrective action? Some quality professionals would say yes... pointing to the stickor the lack of a clear smooth bike path, as the "root cause" of the problem+
 ===== Common Cause vs Special Cause Variation ===== ===== Common Cause vs Special Cause Variation =====
  
-In reality, small sticks and stones appear regularly and randomly throughout open bike paths. Assuming ​that there has not been any unusually windy weather conditions, this is "​Common Cause" variation inherent within the activity of riding along open bike trailsIn factcommon cause variation is defined as "​natural pattern"​ in the process, which is a usual, historical, quantifiable,​ random variation in the process with __NO assignable root cause__. +Imagine ​that you frequent ​particular restaurantThe service and food are typically greatbut occasionally you find that the silverware (rolled in napkin) ​is missing ​piece... or has two of the same piece while missing ​the third piece (e.g.two forks and no knife)Whenever this happens, you simply inform ​the server, who immediately provides you another napkin neatly rolled around all of the required silverwareThe "nonconforming" ​condition is quickly and easily corrected.
- +
-And before you think "trees are the root cause" ​or "the wind is the root cause"recognize that these are "​normal"​ conditions along open bike trailsWhile these conditions could be eliminated through enclosing ​the bike trail... at that point it would cease to be an "open" ​bike trail.+
 <WRAP round box 350px right> <WRAP round box 350px right>
 |  **Common Cause** ​ | usual / normal\\ quantifiable,​ random variation| |  **Common Cause** ​ | usual / normal\\ quantifiable,​ random variation|
 |  **Special Cause** ​ | unusual / abnormal,\\ not previously observed,\\ non-quantifiable variation ​ | |  **Special Cause** ​ | unusual / abnormal,\\ not previously observed,\\ non-quantifiable variation ​ |
 </​WRAP>​ </​WRAP>​
-Howeverhad there been an unusual condition leading ​to excessive debris on the bike train (e.g., such as high winds or a tornado through ​the area)then this would have been a "​Special Cause" variation (i.e., an "​unnatural pattern" ​in the processwhich is unusual, not previously ​observednon-quantifiable ​variation in the process __with an assignable root cause__). Special causes produce systematic effects/​errors in a process. ​  +The staff is well trainedand 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 
-   + 
-Because ​far too many quality professionals fail to differentiate between "​Common Cause" and "​Special Cause" variations in a process, a very large number of nonconformities from "​Common Cause" variations are incorrectly addressed through the corrective action process. This leads to a cycle resembling the 1976 arcade game, "​Whac-A-Mole"​ (where moles pop up from their holes at random, and the player earns points by forcing them back into their hole through hitting them directly on the head with a mallet). In the end, nothing is accomplished... ​but the player ​has a false sense of accomplishment reflected by their score. In this case, the quality team "​feels"​ good (a false sense of accomplishment) about the apparent (short term) success of each corrective action.+Howeverone night you arrive and order dinner only to find that the food takes much longer than normal to arrive at your tablehas been over-cooked,​ and is coldYou complain to the server who apologizes explaining that their chef is unexpectedly absent tonight due to an illnessAnd that this was terrible timing because his Assistant chef is traveling on vacation. Consequentlya replacement chef, who is unfamiliar with both their kitchen and menu, had to be brought ​in to fill this temporary need.  
 + 
 +Unlike ​the silverware issuethis is an unusual ​/ abnormalsituation that has not previously ​occurred. Thereforethis would be a “special cause” ​variation in their process __with an assignable root cause__). Special causes produce systematic effects/​errors in a process. 
 + 
 +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 the following table as "​**Examples of common-cause and special-cause variation**"​. 
 + Process ​ ^  Common Cause of Variation ​ ^  Special Cause of Variation ​ ^ 
 +| Baking a loaf of bread  | The oven's thermostat allows the temperature to drift up and down slightly. ​ | Changing the oven's temperature or opening the oven door during baking can cause the temperature to fluctuate needlessly. ​ | 
 +| Recording customer contact information ​ | An experienced operator makes an occasional error. ​ | An untrained operator new to the job makes numerous data-entry errors. ​ | 
 +| Injection molding of plastic toys  | Slight variations in the plastic from a supplier result in minor variations in product strength from batch to batch. ​ | Changing to a less reliable plastic supplier leads to an immediate shift in the strength and consistency of your final product. ​ | 
 + 
 +As shown in the above examples, a control chart isn't always needed to differentiate between a "​Common Cause" and "​Special Cause" variation. However, because ​far too many quality professionals fail to differentiate between "​Common Cause" and "​Special Cause" variations in a process, a very large number of nonconformities from "​Common Cause" variations are incorrectly addressed through the corrective action process. This leads to a cycle resembling the 1976 arcade game, "​Whac-A-Mole"​ (where moles pop up from their holes at random, and the player earns points by forcing them back into their hole through hitting them directly on the head with a mallet). In the end, nothing is accomplished... ​other than the player ​feeling ​a false sense of accomplishment reflected by their score. In this case, the quality team "​feels"​ good (a false sense of accomplishment) about the apparent (short term) success of each corrective action. 
  
-Only through first determining whether each nonconformity is a "​Common Cause" or "​Special Cause" variation, can "​real"​ corrective action can be realized. 
 ===== Reactive vs. Proactive Process Improvement ===== ===== Reactive vs. Proactive Process Improvement =====
  
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 ==== Proactive Process Improvement ==== ==== Proactive Process Improvement ====
  
-Because "​common cause" variations are inherent to the existing process, these variations can only be eliminated by significantly "​modifying"​ or "​re-designing"​ the existing process. The most effective process improvement activities are realized through applying the Lean Six Sigma concepts & methodologies.+Because "​common cause" variations are inherent to the existing process, these variations can only be reduced or eliminated by significantly "​modifying"​ or "​re-designing"​ the existing process. The most effective process improvement activities are realized through applying the Lean Six Sigma concepts & methodologies.
  
 As a process is being "​modified"​ or "​re-designed",​ one of the best tools to use is the [[https://​asq.org/​quality-resources/​fmea|"​Failure Mode and Effects Analysis"​ (FMEA)]]... or FMECA ("​Failure Mode, Effects and Criticality Analysis"​). As a process is being "​modified"​ or "​re-designed",​ one of the best tools to use is the [[https://​asq.org/​quality-resources/​fmea|"​Failure Mode and Effects Analysis"​ (FMEA)]]... or FMECA ("​Failure Mode, Effects and Criticality Analysis"​).