5 Whys

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The 5 Whys is a simple approach to help a team identify underlying reasons for a problem.

What is it?

By repeatedly asking the question ‘Why?' (use five as a rule of thumb), you can peel away the layers of an issue, just like the layers of an onion, which can lead you to the different root causes of a problem.

The reason for a problem can often lead into another question; you may need to ask the question fewer or more than five times before you get to the origin of a problem.

The real key is to avoid assumptions and logic traps and encourage the team to keep drilling down to the real issues that underlie why different factors have aligned to contribute to something going wrong.

What does this tool look like?
Image shows an example of the tool
Why use this tool?
  • Helps you to identify a set of underlying causes of a problem.
  • It is easy to learn and apply and provides a visual way to share thinking.
  • It can help you to develop ideas for how to change the system to reduce the chances of the problem happening again
Where does this tool fit in the improvement journey?


This tool is relevant at this stage of the Quality Improvement Journey.


This tool is relevant at these stages of the Quality Improvement Journey.

How to use it.

It is most helpful to use this tool in a group and to then share it with others to start to identify possible changes to test.

  • Write down the specific problem. Writing it down helps you formalise the problem and describe it accurately. It also helps a team focus on the same problem.
  • Use brainstorming to ask ‘Why?’ the problem occurs then, write the answer down first.
  • If this answer doesn't identify the source of the problem, ask ‘Why?' again and write that answer down.
  • Some of the Whys may be part of the same issue so think about how you might group these together.
  • There will often be more than one cause, so repeat the process as many times as you need to. It can also be helpful to use this in conjunction with cause and effect analysis to help explore the different types of causes.
  • You can then think about possible change ideas that will help with the identified causes.  See the topic on developing change ideas.