Thursday, January 10, 2008

5 Whys: To get better, say "why?"

If you have a 2 year old, or remember them, you are familiar with the word "why". Repeatedly. Now, a more adult way to use that word.

Lean tells us we should ask "Why" all the time. In fact, the 5 Whys. To discover the root cause of a problem. So we fix it once and for all.

Here's how Taiichi Ohno explains it:
It is difficult to do even though it sounds easy. For example, suppose a machine
stopped functioning:

1. Why did the machine stop?
There was an overload and the fuse blew.

2. Why was there an overload?
The bearing was not sufficiently lubricated.

3. Why was it not lubricated sufficiently?
The lubrication pump was not pumping sufficiently.

4. Why was it not pumping sufficiently?
The shaft of the pump was worn and rattling.

5. Why was the shaft worn out?
There was no strainer attached and metal scrap got in.

Repeating why five times, like this, can help uncover the root problem and correct it. ...get the real cause...which is often hidden behind more obvious symptoms.

Do you ask the Five Whys every time you have a bug in your software?

To hear further explanation from Taiichi Ohno, see chapter 2 of his short book:

There are many other great ideas in this book.

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