The Art of Root Cause Analysis

Five whys analysis to ask the
right questions at the right time

by Vidyasagar A

This article was featured in January 2016’s Best Of Back to Basics edition.

Root cause analysis reminds me of the intriguing mind of a child: Both use common questions that start with "what," "how" or "why" in an attempt to understand something and uncover answers.

Children often satisfy their curiosity as they ask questions to better understand their environment. You could say that they’re already unknowingly using a simple, yet essential quality tool—five whys analysis—to clarify their own questions and get to the truth.

If five whys analysis is used in science to achieve a clear objective, the tool can be just as powerful in the business world as it is for children exploring their own surroundings. As a practicing Master Back Belt, I often use this technique to successfully arrive at the root causes of problems.

What’s five whys analysis?

Five whys analysis is the art of systematically drilling down to a real root cause (see Figure 1). It’s a simple, yet effective way to determine the root causes in almost any situation. Essentially, you can find the root cause of a problem and show the relationship of causes by repeatedly asking the question, "Why?"

Does this remind you of the lean tool TRIZ, or the theory of inventive problem solving? It should, because they can complement each other well.

Online Figure 1 shows a simple example of five whys analysis of "Getting caught speeding on the road." This particular example captures just one answer for every why question asked. Typically, you would have more than one answer for every why question, and each one could be subjected to another why question.

Online Figure 1

Applying five whys analysis

You could say five whys analysis is the art of asking the right question at the right time. In Online Figure 1, it’s important not to skip levels of questions or hurry through them to reach a perceived root cause. You must approach this analysis step by step with logical questions summarizing the observations from earlier questions.

Figure 1

Don’t get too caught up with asking five questions. Sometimes, it may take just three why questions to reach the root cause. Other times, it might take many more. Once, I had to ask 14 whys to reach a root cause. As you master the art of questioning, you will arrive at the root cause much more quickly.

Things to remember

It’s important not to leave any loose ends. Each loose end must be tied up with a fresh why question, or it should become part of another question being asked.

Another critical point in this analysis is knowing when to stop asking why. Some experienced practitioners say that you have reached the true root cause when the answer to your why question is a process, policy or a person. Often, these answers turn out to be the real root causes.

Knowing when to stop mostly depends on three questions:

  1. How relevant are the questions and answers to the original X or Y you are investigating?
  2. Did you find a root cause that helps you control or avoid the situation?
  3. Are the questions and answers significant enough, considering your project scope?

The real problem

When and where to stop questioning why is the most important part of this approach: Do not stop unless you reach a process, policy or a person that seems to be a root cause. Often, there can be many root causes with a compounding impact placed at different stages of the five whys drill-down.

It is also important to recognize that the real problem in a Six Sigma project is not that we don’t know the solutions. The real problem is that we don’t know real root causes.

Often, some X’s might not have further data to further drill down using Six Sigma tools. Hence, using five whys analysis is almost essential in Six Sigma implementation. Correctly using this technique can be a big differentiator for the project.

Vidyasagar A is the corporate master coach at Genpact in Hyderabad, India. He holds a master’s degree in management from the Indian Institute of Management.

Excellent article....
--Vijay Singh Parmar, 12-03-2015

A great summary of a truly critical skill!
--Daniel C Conrad, PhD, CRE, 10-15-2015

In any RCA investigation the most important tool is; How safe does the person being questioned feel? If there is a feeling of jeopardy for their job getting a true answer to your why may not be forthcoming. The person being questioned needs to know and feel safe in giving their response.
--Walter Rohrig, 09-01-2015

Aylin, I guess i mentioned in the article that It need not always be 5 Whys. It could be more or much lesser than 5. The whole art of Root causing is to KNOW when to ask WHAT and in what direction to delve for root cause. Another helpful thing is to recognize when a real root cause surfaces. More often than not, real root cause is either a Process, Policy or Person. Your judgement is really critical to master this art. Hence this is an ART and not a science :-)
--Vidyasagar A, 08-21-2015

is there a particular; scientific reason; why "why" is repeated 5 times; but not more or less times
until finding real root cause.

Aylin N. Sener
--Aylin N. Sener, 06-24-2015

I appreciate the authors comparison to six sigma. I have never participated in six sigma project but always believed that the two were similar in some ways.
--Nikki , 06-04-2015

It must be noted that the “Five Why” tool only works if the right people are in room. If at least one person is not able to answer the question why, then the team will soon become stuck. Often times the answer to why is not forthcoming. This is usually due to a lack of understanding or involvement by the team members and so the question remains unanswered. When this takes place more investigative efforts and analysis are required.
--Stephen Okon, 02-12-2015

Value of reading some topics or articles never diminish, no matter how many times you repeat. This is one of them. Well written, short, and complete article, capturing both strength and weaknesses in the practice and/or application of the technique, without losing the positive tone. Thank you!
--N. Ravi, 02-09-2015

--Sharmila P, 02-07-2015

Excellent article. I would appreciate the authors comments on acceptance criteria for root cause.
--James aubele, 02-07-2015

Amazingly simple yet very helpful to bring home the concept and make it usable!! Thanks a lot Vidyasagar A.
--OD, 02-06-2015

--William R. Corcoran, PhD, PE, 02-06-2015

Best 5 Why article I've seen!

I would appreciate the author's views on:

What are the qualitative and quantitative acceptance criteria for a "real root cause?"

What are the qualitative and quantitative acceptance criteria for a proper set of "subcauses?"
--William R. Corcoran, PhD, PE, 02-06-2015

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