The 5 Whys technique is a simple to understand, yet difficult to master, tool used in Lean and Six Sigma to understand the root cause of an event. In the most basic sense a practitioner would ask a subject matter expert “why” five times to move from the high-level symptom of a problem to the basal root cause.
A common warning from experts in this technique is to avoid thinking of 5 as some sort of magical number. The number of times that why is asked is arbitrary. Practitioners should avoid asking a set number of questions and concentrate instead on mastering an understanding of when a root cause has been found. This can be especially difficult to master. A practitioner must learn to trust their instincts.
Another common issue with the approach is in choosing which question to ask next. Asking the wrong question can send the process in an inefficient direction. This is another area that is difficult to master. Intuition and experience will play a crucial role. The key to being successful overcoming this pitfall is persistence. It may be inefficient to go down the wrong path of questioning, but discovering the root cause is more important than the path you take to get there. Learn from the experience and improve your instincts with every iteration of the process.
One pitfall that is not as commonly explored, but highly impactful in the practice of Lean and Six Sigma in the services industry centers around how the question is formed. Lean and Six Sigma for manufacturing typically revolve around machine processes; whereas Lean and Six Sigma in the services will more frequently concentrate on a human process. This fact can have a significant impact in the method’s success.
Asking questions that start with “why” can cause a highly emotional response. This is especially true if the practitioner is asking a person why they did something versus why something happened with a machine. Imagine the response someone would give if you asked them, “Why did the machine stop working?” They will likely give you a specific symptom that resulted in machine failure. This response will likely be grounded in reason. That reasoned response will allow the practitioner to ask the next question, based on logic and reason that will lead to a root cause.
Now imagine asking a person a similar question, “Why did you stop working?” The response might be based in logic and reason if the person asked has high emotional-intelligence and works in a strong continuous improvement culture; however, most people will be inclined to become defensive and reply from an emotional basis. The subject matter expert in this situation may even feel attacked. This situation will amplify the difficulty of obtaining the root cause of the problem.
To solve this dilemma a practitioner should frame questions based on “what” or “how” rather than “why.” Asking a question that starts with “what” or “how” is generally safer for a subject matter expert to respond to without feeling attacked. This fact will be true in both manufacturing and services, but it will be more common in the services industry.