When should you use 5 Whys?

There is disagreement among the global engineering community as to whether the 5 Whys process is sufficient enough to effectively identify the root causes and ultimately, the solutions, for a particular problem.

Why?

The 5 Whys is a question-asking technique used to explore the cause-and-effect relationships underlying a particular problem. The primary goal of the technique is to determine the root cause of a defect or problem.

The technique was originally developed by Sakichi Toyoda and was used within the Toyota Motor Corporation during the evolution of its manufacturing methodologies. It is a critical component of problem-solving training, delivered as part of the induction into the Toyota Production System. The architect of the Toyota Production System, Taiichi Ohno, described the 5 Whys method as “the basis of Toyota’s scientific approach . . . by repeating why five times, the nature of the problem as well as its solution becomes clear.”

However, whilst the tool may have had success in the automotive industry it has received criticism from within other industries for being too basic and not complex enough to analyze root causes to the depth that is needed to ensure that solutions are identified and the problem is fixed.

However, while the tool may have had success in the automotive industry it has received criticism from within other industries for being too basic and not complex enough to analyze root causes to the depth that is needed to ensure that solutions are identified and the problem is fixed.

There are several reasons for this criticism of the 5 Whys method:

• The tendency for investigators to stop at symptoms rather than going on to lower-level root causes
• Inability to go beyond the investigator’s current knowledge – cannot find causes that they do not already know
• Lack of support to help the investigator ask the right “why” questions
• Results are not repeatable – different people using 5 Whys come up with different causes for the same problem
• A tendency to isolate a single root cause, whereas each question could elicit many different root causes
• Considered a linear method of communication for what is often a non-linear event

Many companies we work with for training and engineering services successfully utilize the 5 Why technique for very basic incidents or failures. By utilizing the correct placement of triggers, organizations can use the 5 Why for its basic problem solving and then move to a form of Cause and Effect analysis like the Apollo Root Cause Analysis method for more complex problems.

A disciplined problem-solving approach should push teams to think outside the box, identifying root causes and solutions that will prevent reoccurrence of the problem, instead of just treating the symptoms.

Any effective problem-solving technique should meet the following six criteria:

1. Clearly defines the problem
2. Clearly delineates the known causal relationships that combined to cause the problem
3. Clearly establishes causal relationships between the root cause(s) and the defined problem
4. Clearly presents the evidence used to support the existence of identified causes
5. Clearly explains how the solutions will prevent recurrence of the identified problem
6. Clearly documents criteria 1 through 5 in a final RCA report so others can easily follow the logic of the analysis

RealityCharting has come up with a simple, free tool that can be used to help with a 5 Why investigation.  RC Simplified,  the free to download version can be utilized on smaller issues as it allows the user to build a cause and effect chart that is no greater than 4 causes high and 5 causes deep. This means the user of a 5 Whys approach can create a Realitychart using the same thought process adopted in the Apollo Root Cause Analysis™ methodology. It also demonstrates a non-linear output to what was originally considered a linear type problem.

So when looking for problem solving tools or root cause methodologies, be willing to “think outside the box” and utilize a number of resources depending on the complexity of the problem and the significance of the incident. We believe that the 5 Why’s approach definitely has a time and place to be utilized. However, if the problem is more complex, don’t limit yourself to a 5 Why approach as you will likely not be satisfied with the solutions generated.