“So” The Art of Reverse Questioning

There are several ways to verify if a root cause is correctly identified. One effective method is to reverse the questioning process. Instead of asking “why” to reach the root cause, we can ask “so?” to trace it back to the potential cause. This reverse approach helps ensure logical consistency and prevents misdirection during root cause analysis. Let’s go through an example to illustrate this concept.

Let’s say we have a problem of motor overheating. The team conducts a root cause analysis and identifies that “the cable was placed too close to a high-temperature machine.”

• Root Cause: The cable was placed too close to a high temperature machine.
  • So? → It was exposed to excessive heat.
  • So? → The power cable of the fan is damaged.
  • So? → The cooling fan is not working.
• Problem: Motor overheated.

In this example, if you start by asking “why?” from the problem “Motor overheated,” you will see that the logic aligns with reverse questioning.

Defect Reproduction

While reverse questioning is a great logical tool to verify, how do we validate that the identified root cause is the real one? The answer is simple: Defect Reproduction.

The best way to validate a root cause is to attempt to reproduce the defect by simulating the root cause. Let’s apply this to our example. We have identified a root cause, but does this really cause the problem? To verify, we can intentionally place the cable too close to a high temperature machine, as stated in the root cause, and observe whether the failure occurs again.

Of course, intentionally causing failures can be costly and impractical. In such cases, we can try to reproduce the defect after implementing corrective actions. Our expectation at this stage is to not see the problem when we simulate it, because corrective actions should provide a permanent resolution.

For example, if we replace the cables with heat-proof ones, even if we place them too close to a high temperature machine, the failure should not occur again. This approach not only indirectly validates the root cause but also confirms the effectiveness of the corrective action.

If you want to learn more about Root Cause Analysis, you can check out my Udemy course