How do you get Root Cause Analysis to work effectively? – Part 2: 5-why analysis


The 5-Why technique was developed by Sakichi Toyoda within the Toyota Motor Corporation and it quickly became a hugely effective root cause analysis tool throughout Toyota and beyond. Taiichi Ohno, who developed the Toyota Production System described 5-Why as “the basis of Toyota’s scientific approach”.

In its simplest form it asks the enquirer to ‘ask why five times’. An iterative approach that’s designed to drill down to fundamental causes of failure, and therefore avoids the often fatal failing of effective root cause analysis of addressing the symptoms instead of the real causes.

Asking why five times! It sounds a bit childish maybe, and it can definitely rub people up the wrong way – but it does work, so don’t dismiss it because it sounds so basic or seems a bit pedantic.

5-Why analysis is a great technique to use:

  • When you have ‘immediate’ and ‘specific’ problems
  • When you have to respond quickly to a problem (especially to customers)

It’s often used as a ‘quick response’ technique for customer quality escapes. I see this technique as a ‘deep and narrow’ analytical method, fix the immediate concern – properly, and in the shortest time possible. You aren’t looking for ‘potential’ causes of failure, you’re only concerned about the ‘actual and immediate’ cause of failure, hence ‘deep’ (understanding) keeping a ‘narrow’ (focus).

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Be aware though that when something fails, it doesn’t just ‘physically’ fail, there’s always systemic considerations that need to be understood too:

  • Why didn’t we NOTICE that this problem occurred – how come we didn’t have an effective inspection process in place before it got to the customer?
  • Why didn’t we consider whether the process could fail or not before we put this process into place?

So there are really three considerations – PHYSICAL, DETECTION and SYSTEMIC

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Think carefully about all three elements of failure and establish why each in turn didn’t effectively contribute to a perfect product or service.

Customers don’t get a product or service until you’ve established the process by which you intend to deliver it, so it’s at this stage that you should ensure all your systems are capable of actually delivering perfection to your customer.

Where your process is fully automated, the likelihood of failure is generally quite small – sometimes even impossible. Where your processes involve human effort, then that’s where you have to give serious consideration to the possibilities of people errors causing defects.

Fact: It’s impossible to have a truly defect free process where human effort is involved. So you have to include ‘checking’ or ‘inspection’ in the process to protect the quality of the end product – and this is always an added cost. Ask yourself, when you’ve ever encountered a physical defect, did you ever find that you had adequate inspection in your process? But also keep in mind, inspection takes time and time costs money – and inspection is often carried out by ….. people!

So, don’t just fix the physical problem – think about what other lessons are to be learned from the experience that can be transferred as best practices into other current processes, and also used as ‘design rules’ for new, to-be processes.

Getting the logic right

Ok, so what about the process of thinking through the physical problem. Couldn’t be simpler… or maybe not!

We all have a natural ‘filter’ mechanism going on in our heads – we naturally filter out the detail that lies in-between a problem and its solution. Consider this problem:

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Obvious, it’s broke – fix it! This is how we naturally think, but sometimes we need to dig deeper, otherwise you’ll quickly be changing another fuse. Consider this then, is this enough…

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I know of some people who would think this is the right solution, but clearly it’s not right is it. The problem isn’t that the switch lets in water, it’s because there’s water in the room. Where’s the water coming from…

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So here we’re digging even deeper based on what we believe is the problem. An expensive solution perhaps – but a solution that will almost certainly stop the problem from happening again.

But what if our ‘theory’ is wrong, what if condensation isn’t the problem after all?

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Here’s an alternative that might be the real reason. Notice here, just like in the real world that there might be more than one real root cause. But in the main you’ll find the majority of problems are a 1:1 relationship with their causes. Just be sure to pick the right solution. These last two examples demonstrate where one fix could cost little and be put quickly in place, but the other fix costs a lot more and will take longer to implement. It’s vital that root causes identified are validated and that you really do choose the right solution, otherwise you’ll be back fixing it again very quickly.

I’ve seen loads of examples in my travels of the wrong (and often expensive) solutions being implemented, purely because the thought process in the root cause analysis wasn’t correct. It’s an acutely embarrassing situation to be in, don’t go there. Remember, this technique is deliberately slowing down the thinking process in order for you to arrive at the right solution.

Get the right people together

The risks of making the wrong call on what the real root cause is can be mitigated by having a ‘team’ approach to problem solving. I could easily ‘guess’ at the outcome of the above – but then again, maybe I’m not the one who knows much about electrics, or about kitchens!

So, we need people from the workplace involved – people who live with the processes every day. Alone, they might not have all the technical knowledge to make the right decision (often they do though!), but get the right people and skills together, and you’ll get the right outcomes.

Remember also that the people in the process will have to live with the changes made. Just try and implement a solution by ‘telling’ the people in the process what they’re going to have to change, and see how long it stays fixed! You must involve the people in the process right from the outset, not just to share real process knowledge, but also to gain buy-in for the changes that will be needed.

So, key messages: how do you get 5-why to work effectively?

  •  5-Why is a ‘reactive’ technique. Fix the immediate problem – quickly
  • There’s rarely just a ‘physical’ problem – always consider how the system influences the physical process
  • Switch off the ‘just fix it’ button when you’re looking for root causes (not as easy as it sounds – especially for technically minded people, but it’s a critical skill to learn in order to succeed)
  • There might be more than one root cause to an immediate problem, but more often than not, problem and root cause are a 1:1 relationship
  • Have a ‘team’ approach to root cause analysis and always involve the people in the process
  • You will NOT get long term solutions if you don’t get buy-in from the people in the process


In part 3 of this series of four articles I’ll explain the background and tricks to effective use of the Ishikawa Cause & Effect analysis technique.

In part 4 I’m going to bring us back to our starting point and explain how all these analysis techniques are really just variations on a theme, and why you shouldn’t be afraid of tackling the more complex analysis tools (once you’ve developed enough capable people to deploy the basics effectively).

If you’ve not already seen part 1 of this series of four articles ‘A bit of background’ by all means feel free to look it up on our blog page.


What sort of strategies do you use to make 5-Why analysis work for you, especially with regard to involving and getting true buy-in from the ‘people in the process’? Why not share your own ideas and experiences about getting the best form this technique.




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