Finding Root Cause is a process
of determining the reason why something occurred. This process is often applied in situations when something breaks, or a failure or defect occurs, but can be applied to any situation where the result is not expected. Root Cause is a subset of Cause and Effect understanding.
Something happens, and someone asks, “How come this happened?"
When the answer isn’t obvious, a methodology of finding Root Cause is often implemented. Root cause determination can be a complicated process, but in many cases, a great place to start is by asking a few basic questions.
One technique, called “The 5 whys?”
was made popular by Toyota. They found that asking “Why?” five times would be sufficient to find the Root Cause. One downside of this process is the answers provided are limited to the knowledge base of those who are answering. Nevertheless, it’s often a good place to start.
We use three tools to begin a Root Cause investigation
; They are “Why?”, “What else?”, and “Possible”
We start with “Why did this happen?”
Someone responds, “Because of ….” You then ask “Why did that occur?” Someone responds, “Because of ….”. You ask again “Why?”.
Here’s an example Root Cause conversation from one of our clients.
"Many of your customers are unhappy" (Problem).
- Why are they unhappy? Because we are not delivering our products on time.
- Why are we not delivering on time? Because we have a backlog in manufacturing.
- Why is there a backlog in manufacturing? Because we can’t make our product fast enough.
- Why can’t we make our product fast enough? Because we don’t have all the parts we need.
- Why don’t we have the parts? Because one of our suppliers didn’t deliver the quantity of parts we ordered"
Supplier didn’t deliver what the contract called for.
; Find another supplier of parts, Increase inventory reserve, move some of our QA to our suppliers site.
Note: When using this method, we are often asked, “How do you know when to stop asking why?” It’s a great question. In the above example, one might have asked, “Why did the supplier not ship the number of parts ordered?” but that’s something that might be beyond your control, so you can’t push the Root Cause analysis to a place that you can’t do anything about. You can however understand that weakness, and look for solutions to compensate for that. You can ask them to find their root cause.
We also use “What else?”
. For example, when someone responds with a “Because ….”, you can follow up with “Is there anything else that can explain why that occurred”. You do this, to explore multiple possible root causes. In the example above, perhaps one explanation for not having the parts is that the inventory ran too low because it was not synced with the forecast.
Lastly, when everyone is out of ideas
, you can present the following question; “What could possibly exist, even if improbable, or seemingly impossible, that could, under certain circumstances, cause this?”. You present this question when everyone is scratching their heads and responding, “I don’t know?” to the Why? or What else? question.
; Finding Root cause is an important process that leads to an understanding of what has happened that produced a particular result. It can help prevent another bad result, as well as replicate a good result. To find Root Cause, start with asking Why? and What Else? If you get stuck at “I don’t know”, then go find someone who does, and also ask the “what is possible” question, to stimulate ideas that are beyond the everyday obvious connections.