Whac-A-Mole Arcade Game

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 I realize that the following is a simplistic, “goofy” example (itself open to criticism), bear with me. Let's assume that on warm summer days, you regularly ride a bicycle along your favorite open bike path. However, on one particular day, your front tire hits a small stick at an awkward angle causing you to fall from your bicycle and break your arm. After your arm is healed, you 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.

Would you consider that to be an effective corrective action? Some quality professionals would say yes… pointing to the stick, or the lack of a clear smooth bike path, as the “root cause” of the problem.

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 a “Common Cause” variation inherent within the activity of riding along open bike trails. In fact, common cause variation is defined as a “natural pattern” in the process, which is a usual, historical, quantifiable, random variation in the process with NO assignable root cause.

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 trails. While these conditions could be eliminated through enclosing the bike trail… at that point it would cease to be an “open” bike trail.

Common Cause usual / normal
quantifiable, random variation
Special Cause unusual / abnormal,
not previously observed,
non-quantifiable variation

However, had 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 process, which is unusual, not previously observed, non-quantifiable variation in the process with an assignable root cause). Special causes produce systematic effects/errors in a process.

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.

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 Process Improvement

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).

Consequently, because “special causes” produce systematic effects/errors in a process, properly implemented “corrective actions” are reactive process improvements… refining an existing process.

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.

As a process is being “modified” or “re-designed”, one of the best tools to use is the "Failure Mode and Effects Analysis" (FMEA)… or FMECA (“Failure Mode, Effects and Criticality Analysis”).