The Five Whys

Process ImprovementBy: Romains Bos

Contents

Root causes The five whys in action Why five? Review

Root Causes

Root cause analysis is a fundamental aspect of continuous improvement

It’s how we figure out the difference between defects and errors – errors cause defects

There are many forms of root cause analysis: Descriptive frameworks Statistical packages Investigative methods

The Five Whys is a simple and proven method for reaching the same conclusions

The Five Whys In Action

A two-week old washing machine suddenly stops working . . .

Why did the machine stop working?

1st Why:

The fuse blew

Why did the fuse blow?

2nd Why:

The motor overheated

Why did the motor overheat?

3rd Why:

The shaft was misaligned

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The Five Whys In Action

A two-week old washing machine suddenly stops working . . .

Why was the shaft misaligned?

4th Why:

The shaft bearing was damaged

Why was the bearing damaged?

5th Why:

Θ

The shaft seal was missing

Why Five?

Obviously, most causes of defects won’t be exactly five whys deep

“Five” promotes persistence, rather than the assumption of simple cause and effect

Don’t stop until you get to the root cause, but once you’ve reached the root cause, stop

Review

Root cause analysis is an important aspect of continuous improvement because it helps us to identify the errors that cause defects

We use the five whys to ensure that we drill down to the root causes of problems

“Five” promotes persistence; most root causes will not be exactly five levels deep