5 Why

5 Why is a systematic process for establishing root causes.  It is important to know root causes as action taken to address root causes (i.e. countermeasures) is more likely to be effective.  Here is an example: 

1. why did Pat break his arm? because he slipped
   

2. why did Pat slip? because there was hydraulic fluid on the floor
   

3. why was there hydraulic fluid on the floor? because the valve on the scissor lift is leaking
   

4. why is the valve leaking? because the gasket is no good
   

5. why hasn’t the gasket been changed? it was changed only two days ago but all the new batch of gaskets have problems
   

6. why do all the gaskets have problems? because we have a new supplier
   

7. why do we have a new supplier? because it offered a cheaper price than the  previous suppler
   

8. why are we buying on cheapest price? because the Board instructed purchasing to reduce costs
   

This example is 8 Whys to get to the root cause.  5 is just an average. 5why is a critical part of LAMDA & the A3 process.

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