Five Whys and a Why Not

One more question could change everything

by Alan Fogle and Edward Kandler

Good ideas can come from anywhere. Recently, a suggestion was submitted through our organization’s employee suggestion program proposing that we modify our five whys-based root cause analysis class to add a sixth level called "Why not?"

The five whys method is a way of drilling down to the root of a problem by stating the problem and asking, "Why did the problem occur?" This first "Why" is followed by asking, "Why did the answer to the first question occur?" This continues until either the root is discovered or the fifth "Why?" question is asked.

By adding a "Why not?" question to the line of questioning, the five whys method can be significantly enhanced while still maintaining the simplicity of the original method.

Equally important to asking the additional question of "Why not?" is the timing of when to ask the question. When presented with a problem in a fast-paced environment, there is a temptation to jump to a conclusion based on a hunch, which could take the form of "Why not just try this solution?"

This bypasses the whole, formal root cause analysis process and will likely result in a superficial solution to the problem. Avoid this tactic at all costs if your goal is to discover the root cause.

By moving the "Why not?" question into the chain of "Why?" questions, it forces the problem solver to test the root cause against the original problem. The question takes the form of "Why might this cause not be the root cause of the problem?"

Changing the thought process

This additional question also forces the problem solver to use a different type of thought. Whereas driving down to the root cause is an exercise in deductive reasoning, the why not exercise reverses the reasoning to one of induction.

This deduction-induction loop becomes a self-check and should bring the team back to the original problem if the true root cause is found. The advantage of the five whys and a why not thought process, relative to the standard five whys process, can be seen in Figure 1.

Figure 1

By forcing an answer to the "Why not?" question at each level of "Why?" questioning the listed cause can be compared to other possible or more likely causes. This can lead to either cause elimination or branching where multiple causes could be present.

It can be argued that the five whys approach to root cause analysis is one of the best tools in the problem-solving toolbox due to its simplicity in execution.

By adding the "Why not?" question to the approach, the thoroughness of the tool is significantly enhanced while maintaining the original simplicity of execution.

Alan Fogle is the director of quality systems and operational excellence at Ultra Electronics, Nuclear Sensors and Process Instrumentation in Round Rock, TX. He has a master’s degree in quality assurance from California State University in Dominguez Hills. An ASQ member, Fogle is an ASQ-certified quality engineer and inspector.

Edward Kandler is a level three technician at Ultra Electronics, Nuclear Sensors and Process Instrumentation. He has an associate’s degree from Cisco Junior College in Texas. Kandler is certified by the American Society of Certified Engineering Technicians.

good ideas.
further; additional clarifications, requirements, etc. such as why not to automatically restrict / reduce / eliminate the deviation / root cause at earlier stages might be a good idea.

Aylin N. M.


This seems like one of those ideas you look at and say: "It seems so simple. How did we not think of this before?" Good article, and interesting approach that I may integrate at my organization. Thank you for sharing.
--Chris Sweat, 05-25-2017

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