The Five Whys is an iterative problem-solving technique developed by Toyota, as part of their Toyota Production System manufacturing method. It is a simple technique where we keep asking Why, at each stage dissecting or deconstructing the answer and often it takes five or more times to drive down to a satisfactory root cause.
It is designed to be a simple technique that anyone can understand; there will often be more then five.
The inventor of the Five Whys technique, and also credited with devising the Kanban organisation method, used this original example:
Why did the robot stop?
The circuit has overloaded, causing a fuse to blow.
Why is the circuit overloaded?
There was insufficient lubrication on the bearings, so they locked up.
Why was there insufficient lubrication on the bearings?
The oil pump on the robot is not circulating sufficient oil.
Why is the pump not circulating sufficient oil?
The pump intake is clogged with metal shavings.
Why is the intake clogged with metal shavings?
Because there is no filter on the pump.
This would fail any modern root cause analysis and manufacturing standards and would probably need a further three or four Whys.
Do not stop, five is a guide.
Why did you miss the meeting?
I was late for work and got a later train.
Why were you late for work?
I woke up late for work.
Why did you sleep late?
My alarm clock didn't go off.
Why did the alarm clock fail?
The battery was flat.
Why was the battery flat?
I was not monitoring it, and did not check the night before.
The root cause is the failure to maintain the clock and the lack of any backup.
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