What it is for: The five whys is a root cause technique: you start with an observed problem, ask why it happens, then ask why that answer is true, and keep going, usually about five times. You leave with a short chain from the observed problem to a likely cause, each step tied to evidence, plus any alternative causes worth checking and one concrete test to run.
Who it helps: Operations, quality and service teams dealing with a problem that keeps coming back, or learning from an incident.
When to use it
When one specific problem keeps coming back after it has been fixed.
When you have a symptom in your data and want a likely cause before choosing a solution.
After an incident, to learn what allowed it to happen.
How to use it
Write the problem as an observation, with a number and a place.
Ask why it happens and write the best-supported answer with its evidence.
Keep asking why, usually four to six times, and log any alternative cause.
Stop where the evidence ends or you reach a cause you can change.
Read the chain backwards with therefore, then agree one test of the cause within two weeks.
Tip: Have the people who do the work in the room. They usually know the answer to the third or fourth why.
Credits and sources: Original Tiremesù worksheet and wording. Method credit: Sakichi Toyoda and Toyota. Further reading: 18F Methods https://github.com/18F/methods/tree/main/_methods
Full guide and film:https://www.tiremesu.com/guides/five-whys
