The "Human Factors" in Cause & Effect Analysis

AS91xx requires “human factors” to be considered when “determining the causes of” a nonconformity. Interestingly, the corrective action process itself (specifically the Cause & Effect Analysis process) is prone to several signficant human factors.

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 associated with being the “cause” of a problem. So “finger pointing” often ensues.

For example, assume that a defective product was shipped and reported by the customer. The records identify the worker who failed to identify the nonconformity… and the Inspector who also failed to identify the nonconformity.

The nonconformity involved a defective component from a supplier. So the worker claims to have not been at fault because component testing testing is not a part of the process. The Inspector claims to have not been at fault because there is no “power on” check of every product shipped. Both point fingers at the Supply Chain Quality Management function, who cites very good past performance from this supplier. While this component had initially been subject to a sample-based receiving inspection, this was loosened followed by giving the Supplier a “Dock-to-Stock” status. Upon contacting the Supplier, the company was informed that the manufacturer of this component is a very good supplier. But they will alert the manufacturer of the defect and issue them a “Supplier Corrective Action Request”. Since this component is only one defect of thousands of produced, the Manufacturer refunded the cost and replaced the defective component. This is stated on their “Supplier Corrective Action Request”… which isn't a “corrective action” at all.

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 branch or parallel causes/effects.

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.

Also, the simple “5 Whys” method only goes to the point of the analyst's “ignorance”… NOT the “Root Cause”. No individual or team, possesses all of the knowledge, skills and experience known to mankind. Therefore, 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”. Consequently, one could easily argue that identifying the true “root cause” of any event is impossible.

In reality, the “Root Cause” identified is often considered reasonable and acted on as if it were the actual root cause. In effect, this is a game of roulette. Sometimes the actions taken will prevent a recurrence of the problem. But the odds are against this action being effective.