5 Whys

Method to identify the real root cause of problems by iteratively asking "why" for the answers. Usually, the first answer does not provide the real root cause. The 5 Whys help to investigate further explanations. Use the fishbone (or Ishikawa) diagram to define possible root causes. Then determine actions and countermeasures. Make sure that similar products/processes are not affected.

Example: Problem = Warehouse is full.

1st Why? Why is the warehouse full? => Because the building is too small.

2nd Why? Why is the building too small? => Because the racks are all full.

3rd Why? => Because we purchase more than we sell.

4th Why? => Purchase batches are bigger than selling batches.

5th Why? => Sales occur on a daily basis, purchases are made on a monthly basis.

Real cause: Purchasing levels are not calibrated to sales volumes.

Action: Define sales volume over one, two, or three months; change frequency of procurement.

Countermeasure: Check stock levels (in terms of purchasing) on weekly basis; Purchasing frequency and amount.

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