Five Why's

Brief Description
The five whys is a simple yet powerful analytical method for understanding the root causes of something that happened. It uses questions to carry out a deep analysis of the cause/effect relationships underlying a particular situation. The method was developed by the Toyota Motor company for mechanical problem solving, but its application is now widespread, including in the field of experience capitalization. It is used by teams in a variety of ways – to look at why problems occurred, but also why any event unfolded in the way it did.

(Again, from Wikipedia)
"The technique was originally developed by Sakichi Toyoda and was later used within Toyota Motor Corporation during the evolution of their 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."[1] The tool has seen widespread use beyond Toyota, and is now used within Kaizen, lean manufacturing, and Six Sigma."

When to use
  • Working to identify the root of a problem
  • When you sense you are not getting to the core of an issue
  • To help yourself/others reflect more deeply on an issue (and perhaps get past assumptions and blind spots)
  • To surface assumptions that may be invisible or unspoken.

(Again, from Wikipedia)
While the 5 Whys is a powerful tool for engineers or technically savvy individuals to help get to the true causes of problems, it has been criticized by Teruyuki Minoura, former managing director of global purchasing for Toyota, as being too basic a tool to analyze root causes to the depth that is needed to ensure that the causes are fixed. Reasons for this criticism include:
  • 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 - can't find causes that they don't already know
  • Lack of support to help the investigator to ask the right "why" questions.
  • Results aren't repeatable - different people using 5 Whys come up with different causes for the same problem.
  • The tendency to isolate a single root cause, whereas each question could elicit many different root causes
These can be significant problems when the method is applied through deduction only. On-the-spot verification of the answer to the current "why" question, before proceeding to the next, is recommended as a good practice to avoid these issues.[2]

How to use
1. Gather the team who will conduct the analysis. If working with a larger group, this can be split into subgroups of 4-6 people. Each group nominates a chair, who formulates and asks the five questions, and a note taker.
2. Agree on the topics to be analysed.
3. Ask the first ‘why?’ question – group members brainstorm their answer.
4. The group chair then asks ‘why?’ about this answer – followed by another brainstorming session.
5. Continue through five rounds (unless the group agrees that it has identified the problem’s root cause in fewer rounds).

Tips and Lessons Learnt
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Examples & Stories
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Who can tell me more?
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Related Methods / Tools / Practices

1. ^ Taiichi Ohno; foreword by Norman Bodek (1988). Toyota production system: beyond large-scale production. Portland, Or: Productivity Press. ISBN 0915299143.
2. ^ "The "Thinking" Production System: TPS as a winning strategy for developing people in the global manufacturing environment". Retrieved 2007-02-20.

method, cause, brainstorming, problem-solving

Photo or image credits
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Page Authors
  • Nancy White