5 Whys:

The 5 Whys is a simple problem-solving technique that helps users to get to the root of the problem quickly. Made popular in the 1970s by the Toyota Production System, the 5 Whys strategy involves looking at any problem and asking: "Why?" and "What caused this problem?"
Very often, the answer to the first "why" will prompt another "why" and the answer to the second "why" will prompt another and so on; hence the name the 5 Whys strategy.
Benefits of the 5 Whys include:
It helps to quickly determine the root cause of a problem
It is easy to learn and apply
How to use the tool:
When looking to solve a problem, start at the end result and work backward (toward the root cause), continually asking: "Why?" This will need to be repeated over and over until the root cause of the problem becomes apparent.
Example:
Following is an example of the 5 Whys analysis as an effective problem-solving technique:
1. Why is our client unhappy? Because we did not deliver our services when we said we would.
Why were we unable to meet the agreed-upon timeline or schedule for delivery? The job took much longer than we thought it would.
Why did it take so much longer? Because we underestimated the complexity of the job.
Why did we underestimate the complexity of the job? Because we made a quick estimate of the time needed to complete it, and did not list the individual stages needed to complete the project.
Why didn't we do this? Because we were running behind on other projects. We clearly need to review our time estimation and specification procedures.
Key Points:
The 5 Whys strategy is an easy and often-effective tool for uncovering the root of a problem. Because it is so elementary in nature, it can be adapted quickly and applied to most any problem. Bear in mind, however, that if it doesn't prompt an intuitive answer, other problem-solving techniques may need to be applied.