iSixSigma

5 Whys

Definition of 5 Whys:

The 5 Whys typically refers to the practice of asking, five times, why the failure has occurred in order to get to the root cause/causes of the problem. There can be more than one cause to a problem as well. In an organizational context, generally root cause analysis is carried out by a team of persons related to the problem. No special technique is required.

An example is in order:

You are on your way home from work and your car stops:

  • Why did your car stop? Because it ran out of gas.
  • Why did it run out of gas? Because I didn’t buy any gas on my way to work.
  • Why didn’t you buy any gas this morning? Because I didn’t have any money.
  • Why didn’t you have any money? Because I lost it all last night in a poker game.

This example should illustrate the importance of digging down beneath the most proximate cause of the problem. Failure to determine the root cause assures that you will be treating the symptoms of the problem instead of its cause, in which case, the disease will return, that is, you will continue to have the same problems over and over again.

Also note that the actual numbers of whys is not important as long as you get to the root cause. One might well ask why did you lose all your money in the poker game last night?

Here’s another example. The Washington Monument was disintegrating

  • Why? Use of harsh chemicals
  • Why? To clean pigeon poop
  • Why so many pigeons? They eat spiders and there are a lot of spiders at monument
  • Why so many spiders? They eat gnats and lots of gnats at monument
  • Why so many gnats? They are attracted to the light at dusk.

Solution: Turn on the lights at a later time.

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