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Lean Manufacturing

5 Whys Problem Solving

Lean Manufacturing Tools and Techniques

Lean Manufacturing 5 Whys

The 5 Whys is a problem solving technique aimed at finding the root cause of an issue. Pioneered by Toyota, 5 Whys is a very simple method, yet it can be highly effective. The basic idea is to solve problems by continuing to ask ‘Why?’ (at least 5 times) until you get to the root cause. What this does is enable any corrective action to fix the problem to be aimed at the underlying issue, rather than focusing on short term fixes which typically target the symptoms.

In short then, 5 Whys encourages a questioning mind-set. When problems occur employees shouldn’t just rush to the quickest solution, which often only addresses the symptoms. Instead keep probing until you discover the real issue.


In a manufacturing environment 5 Whys is particularly effective as it can quickly unearth the cause of defects or quality problems. The technique also has the advantages of encouraging teamwork and collaborative problem solving. In addition, it is quick, low cost (only time) and because it is so simple, it requires very little training and so is likely to keep employees engaged.

Practical use of 5 Whys may involve assembling a group with complimentary skills and getting them to run through the 5 Whys for a known problem. It involves documenting their ideas, perhaps on a white board. This is recommended because one limitation of 5 Whys is the potential to go off on the wrong tangent and potentially draw the wrong root cause conclusion, if you are not correct about the true cause of one of the Whys.

The advantage of assembling a knowledgeable group is it increases the likelihood of obtaining honest answers to the Why? questions. This is because the group is collectively more likely to remember issues, as well as challenge and scrutinise the answer to each ‘Why?’ question.

The team should use a variety of searching questions to scrutinise the answers and so find the root cause. Examples include, asking if there are a range of causes that could produce the problem, as well as what evidence there is the agreed answer is the root cause? Also, has anything like this happened before?

The experience of those assembled will also clearly play a significant part.  Once the root cause has been established, the group can then start identifying potential solutions. These can then be reviewed in terms of cost, time and practicality, before being implemented.

Lean Manufacturing 5 Whys


5 Whys Root Cause Problem Solving Tool: Training Video (courtesy of Valaction Videos) 


5 whys - The Path to Resolution from Tor Ivry

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