Why the ‘5 Why’s’ are not enough for a good investigation


By: John Westphal


Event Investigation is a tool within the reactive learning system that we use to extract learning from an event. One of the practices I have employed as a six sigma black belt and human factors investigator is the ‘5 Whys’ technique. It is used in the Analyze phase of the ‘Six Sigma DMAIC’ (Define, Measure, Analyze, Improve, and Control) methodology, and is a technique that seeks to identify the root cause of an event.

That said, as organizational leaders, I believe we have become overly captivated with the identification of the root cause. Many organizations have fallen into the trap of believing if they find the root cause, they have in essence found the piece to address for further mitigation of the event risk. This, in my experience, leads us down a path of fixing one event at a time rather than addressing common cause failures, which are often further up the causal chain and allow us the opportunity to address risk in a more holistic fashion.

The ‘5 Whys’ is a simple methodology that allows us a basic understanding of the initiating event (root cause), but as we seek to extract all the learning from the event for more effective risk mitigation, we must employ additional methodologies (Rules of causation) to help us understand the cause and effect relationship, mitigate the use of negative descriptors that are subjective in nature, identify and explain the human errors and at-risk behaviors within the event, and lastly, only allow causal factors that had a preexisting duty to act.

It is from the place of a more sophisticated event analysis that we can filter the noise around the event and better understand the role of human error, at-risk behavior, mechanical failure, and environmental/cultural conditions that increased the likelihood of the event. Armed with a more sophisticated approach to reactive learning, we now have the opportunity to classify the failure. In other words, was this design failure, component failure, or unique failure? Depending on which we see dictates the response to the event, thus safeguarding the organization from overreacting to single events.

Now that we have the failure classified with a good understanding of the direct and probabilistic causal links within the event, we are in a better position to conduct the systemic analysis across multiple events, searching for the common cause failures.

It is at this point we have now converted our reactive learning system to a proactive learning system, breaking causal chains across multiple events, decreasing the risk throughout our operational environment.

We can see that, although the ‘5 Why’s’ is a simple tool that allows us a very basic understanding of an event, it is simply not enough for a good investigation that makes it possible to convert the learning system from reactive to proactive and eventually predictive in nature.

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