5 Whys tool in Root Cause Analysis(Explained with examples)

Learn the concept of 5 whys or why why analysis with the help of examples. 5whys is a very simple and easy to learn tool but it is very effective in root cause analysis. It is a team exercise and can be used after doing the brainstorming activity.
Tool Description

The five whys uses a systematic questionnaire technique to search for root causes of a problem. The technique requires participants to ask “why?” at least five times, or work through five levels of detail. Once it becomes difficult to respond to “why?,” the probable cause may have been identified.

This root cause analysis tool asks “Why” multiple times and places the answers in a tree diagram structure until the question is exhausted. Sometimes, it is useful to ask several ‘What’s before asking why – in order to ensure that causes are being addressed rather than symptoms. The team keeps asking itself “WHY?” until there is consensus that the last answer provides a real explanation, that cannot be further partitioned.

In this example, four potential root causes have been identified. These potential causes may be entered as small bones on the Fishbone diagram.


“Why-Why” Analysis helps to structure brainstormed ideas towards problem root causes.
When to Use it When the team needs to explore possible root causes and represent them on a single diagram.

How to Use it

1. State the problem to be analyzed.

2. Ask “Why” – i.e.. what are the first level of causes of the problem?

3. Write each cause on the diagram.

4. For each cause, ask “Why” again and write the answers in the next column, linked to the previous answer.

5. Keep asking “Why” until no more answers can be suggested.

6. Use the causes listed, especially those on the last level of the diagram, to generate possible solutions.

7. Review data for evidence of which causes are most important; gather fresh data if necessary.

Example of 5 Why’s