Five times Why Root cause analysis

The Five Whys is a root cause analysis technique used to identify the underlying cause of a problem by repeatedly asking "Why?" — typically five times — until the root cause is found.

Simply put: Start by stating the problem, and then ask Why?.
For the answer, you come up with, ask Why? again.

Repeat this process five times, or as often as possible. In practice, you may reach the root cause in fewer or more than five iterations — five is a guideline, not a strict limit. The final answer comes closest to the heart of the problem and is therefore called the root cause of your problem. 

The root cause often relates to a particular problem or the lack of a particular process. When you solve the root cause, you can prevent the problem from recurring.

Once the root cause is identified, document your findings and implement a corrective action — such as creating a new process, updating a procedure, or assigning ownership — to address it systematically.

Example

Problem

Peter almost got hit by a forklift.

Five times why

1. Why did Peter almost get hit by a forklift?
   Answer: Because he walked off the pavement.
2. Why did Peter walk off the pavement?
   Answer: Because pallets were blocking the pavement.
3. Why were pallets blocking the pavement?
   Answer: Because there were old markings on the street. The operator who placed the pallets there was new and didn't know this spot was no longer in use.
4. Why were there old markings on the street?
   Answer: Our Technical Service forgot to remove the old markings.
5. Why did our Technical Service forget to remove the old markings?
   Answer: Markings are supposed to be logged; there is no procedure in place for how and how often the log file should be updated.

So in this example, there is no procedure for updating the log file on markings. If such a procedure is agreed upon and respected, the chance of erroneous markings becomes much smaller.