Five Whys is a simple brainstorming tool to get to root cause.
It's usually done within a group.
The technique was developed by Sakichi Toyoda.
Often, when we have a problem and we try to fix it, we're only addressing symptoms.
We have to dig deeper to get to root cause by asking why.
We have to peel back the layers.
There's nothing magical about five; you might reach root cause with three whys,
or it might take more than five,
but the idea is to keep digging until you can't go any deeper.
Here is an example.
Our problem is that we've been getting a large number of defects from one supplier.
Why are we getting so many defects?
An initial investigation revealed that parts are being damaged in shipping.
Why are they damaged in shipping?
Because the packaging does not protect them adequately.
Why is the packaging inadequate?
Because the supplier received no guidance on packaging.
Why did we not advise the supplier about packaging?
Because our packaging specifications are incomplete,
so they have not been available to the supplier.
So the lack of specifications was the root cause.
Here's another example; this is an automotive problem.
Started to go to work in the morning, and my car wouldn't start.
Why?
Because the battery is dead.
It would be easy to stop right there and go buy a battery,
but we need to dig a little deeper.
Why is the battery dead?
Because the alternator was not charging it.
Why was the alternator not charging?
Because the belt is broken.
Why did the belt break?
Because I did not do the necessary preventative maintenance.
That is the root cause.
If we had stopped anywhere short of that, it's likely the problem would have recurred.
Here is a manufacturing example.
We have a machining center that requires cooling,
but the coolant suddenly stopped flowing.
Why?
A quick investigation revealed that a circuit breaker had tripped.
Why did the circuit breaker trip?
Because the pump had overloaded.
Why did the pump overload?
Because metal chips got into the pump.
Why did metal chips get into the pump?
Because a metal screen meant to keep them out was missing.
Why was it missing?
Because preventative maintenance was done incorrectly and the screen was left off.
Why was preventative maintenance done incorrectly?
Because we did not do proper training and documentation.
That is the root cause.
I don't know how much truth there is in this old story,
but it's a good illustration all the same.
It seems that the Washington Monument was deteriorating
and it seemed to be happening rapidly.
Why was this happening?
Well, we've been using harsh chemicals and cleaning it frequently.
Why was it cleaned so frequently?
Because there are a lot of bird droppings and they accumulate quickly.
But why are there so much bird droppings?
Birds are attracted to the monument to eat the spiders
that seem to live there in great numbers.
Why are there so many spiders?
Because they eat other insects that gather at the monument at dusk.
Why are insects attracted to the monument at dusk?
Because the lighting attracts them.
The solution, or at least part of it, was to turn the lights on later.
These examples are meant to illustrate just some of the ways
that the Five Whys can be used to find root cause.
Remember, this usually works best with a group
and there's nothing magical about the number five.
Sometimes it will take more than that; sometimes it will take less.
You just need to keep digging until you cannot go any further.