The 5-Whys is a problem-solving method for exploring the cause-and-effect relationships underlying a problem. The goal is to determine the root cause of a defect or problem by repeating the question “Why?” five times. The 5-Whys was developed by Taiichi Ohno, the father of the Toyota Production System.
The specific number five is not the point. Rather it is to keep asking until the root-cause is reached and eliminated.
5 Whys is problem-solving that focuses on:
- root cause analysis
- problem definition
- setting goals
- establishment of countermeasures
- checks, standards, and follow-up activities
There are three types of root-cause analysis:
- logic
- one-variable-at-a-time (OVAT)
- multivariate-at-a-time (MVAT)
Criticism of 5 whys include:
- tendency to stop at symptoms rather than root causes
- inability to go beyond the investigator’s current knowledge
- lack of support
- different people come up with different causes for the same problem.
- tendency to isolate a single root cause, instead of many different root causes
- artificial reliance on 5 whys
- distortion to favor new features instead of a root cause analysis
5 Whys is a tool that helps to arrive at a root cause. Not only can the root cause be identified but second-order consequences can also be unearthed.