5 Whys
Ask why of the answer, five times, until you reach a cause you can actually act on.
Best for a Problem · Toyota, 1950s · takes ten minutes
How to run it
- Write the problem as one observed fact. Not "the band is flaky" but "we have missed four of the last six practices". Say how you know.
- Ask why it happened. Write one answer, a cause you could check, not the same event in other words.
- Ask why of that answer, not of the original problem. Write the next answer beneath it.
- Keep going. Whenever the answer is a person’s mistake, ask why the mistake was possible, or why it mattered.
- Stop when you reach something you could change tomorrow. Five is a guide, not a rule. Three is often enough, and if the fifth still isn’t something you can act on, the chain went sideways: start again from the first why.
- Write the change as an action. Then check it backwards: if that had been in place, would the chain have broken?
Where it falls down. It assumes one chain of causes.
With a pen
The problem, as an observed factWhat went wrong, and how do you know
Why did that happen?Because... a cause, not the event in other words
And why did that happen?Asked of the answer above
And why did that happen?Can you act on this cause? Yes: root cause. No: redo from the first why
The fix that breaks the chainSomething you could change tomorrow