5 Why method

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The 5 whys , even 5W method or shortly 5 Why or 5W called, is a method in the field of quality management for the cause-effect determination. The aim of this application of the five “why?” Questions is to determine a cause of a defect or a problem. The number of inquiries is not limited to five, this number is to be understood symbolically. It is important to continue checking until the process step causing the error is clearly identified and can no longer be divided up. This can be done e.g. B. check by reversing the causal relationship. Toyoda Sakichi is considered to be the inventor of this method.

example

Problem: The vehicle does not start.

  1. Why doesn't the vehicle start?
    The starter battery is empty.
  2. Why is the starter battery empty?
    The alternator does not work.
  3. Why is the alternator not working?
    The V-belt is torn.
  4. Why did the V-belt break?
    The V-belt was never changed.
  5. Why was the V-belt never replaced?
    The vehicle has never been serviced before.
  6. Why was the vehicle never serviced?
    A maintenance interval was not prescribed.

See also