In lean, the best thing to do is to keep things simple, so here are the top lean tools for root cause analysis. I could bore you to death with a dearth of tools, techniques and frameworks, but we’ll take a pragmatic view and i’ll show you the best and most popular… Which won’t take any six sigma qualification to understand.
What are the common lean tools for root cause analysis? The most common and widely used lean tools for root cause analysis are Pareto charts, Fishbone diagrams, and the 5 why problem solving technique. They can be used individually or together in a deeper dive activity, to help uncover process failures and root causes to problems.
Each has a role to play and in the following guide, i’ll show you how they fit together and how you can implement them effectively.
Lean Tools for Root Cause Analysis: The PDCA Framework
Lean and root cause analysis fall within the general framework of the PDCA model. PDCA stands for Plan-Do-Check-Act.
It’s a systematic way of making improvements. And when we’re dealing with problems, it’s a very robust way of working. Think of lean problem solving as improvements built around a scientific method. This scientific method is the PDCA framework.
The Scientific Method
Making improvements and getting to root causes of problems requires data and observation. In science, the process is very prescriptive.
Here’s how it works.
A theory often exists.
- With this theory, the scientist can infer what should happen when they run an experiment. And by planning the experiment and what they think should happen, they either prove or disprove the theory. This is the Plan phase of PDCA.
- They then run the experiment to test the theory and hypothesis. This is the Do part in PDCA.
- They check the results and cross reference what they expected to happen based on what they currently know (the theory). This is the Check phase
- They then act based on the results. In this case, they confirm the results behaved as expected, or they didn’t, therefore challenging if the theory stands up. This is the Act Phase.
It’s why Einstein’s theory of relativity still stands the test of time. Many people have run experiments, to trial the theory, and none have failed in experiments, yet.
PDCA in the Business Sense
In root cause analysis, this approach is no different.
- A problem has been identified. The team then create a theory of what is happening and why. They then create a plan to eliminate this theoretical root cause and test it on a small scale. (Plan phase)
- The improvement action to tackle the proposed root cause is initiated and tested. (Do phase)
- The team then observe and check to see if the improvement idea has worked. (Check phase)
- The improvement either worked or it didn’t. If it did, this improvement then becomes the new standard and rolled out as a process fix. If it didn’t they’ve learned a little more about the process and try another improvement idea, repeating the PDCA process until the problem doesn’t return. (Act phase)
This PDCA model is used in lean businesses, every day and is a very structured way of eliminating root causes.
There are tools to help drill down and provide clues as to what potential root causes to go after and get the PDCA wheel rolling. But the PDCA framework is the model to follow when going from problem to resolution.
Pareto charts are a very effective way of identifying the vital few issues that affect the majority results.
The Pareto principle suggests that 80% of issues come from 20% root causes. Now, the numbers are not exactly this in all walks of life. It could be 75% – 25% or even 95% -5%, but the point is, the majority of outputs are effected by the minority root causes.
Test this out for yourself.
- The majority of sales come from a select few customers…
- The majority of sales targets come from the few high attainers…
- the majority of your issues come from a small number of customers
With Pareto, we can use data to help understand our processes. We can answer how they’re performing and identify where to focus our root cause analysis efforts.
Here’s an example:
In the above, now we’ve sorted our data, it’s a lot easier to know what to work on with priority. Issues from the customer changing their mind and breakdowns should be the primary focus, rather than wasting time on the reasons for running out of stock.
How to Implement Pareto
- Write down the potential top level causes for failures in your process. Stick to no more than 7. We don’t want to go too deep yet. We just need to know where to point our focus.
- Create a simple chart, either on Excel or a white board and get the team to record the number of times each issue raises its head.
- Keep tracking until you have some meaningful data.
- This will then form the basis of the next step in root cause analysis – Drilling down further, to identify the root causes.
You can even create another Pareto chart to track the main causes for the customer changing their mind and what each machine breakdown was. This use of Pareto charts can have a big impact in narrowing focus, quickly and using data, rather than opinions.
(Remember, we want to keep our problem solving as data driven and scientific as possible)
The next step in the root cause analysis journey is to identify as many potential causes the team can think of, which affect the topic in question.
We can use the Pareto charts here to give us areas to focus and then break each one down using individual Fishbone Analysis .
It’s called a fishbone because the diagram represents a fishbone and a head:
In the Fishbone model, ideas are captured around the different topics. The default ones are method, environment, machine, material and man.
Questions are asked: “what could cause the effect (at the head of the diagram)?
The team brainstorm as many ideas as possible until they’ve exhausted all ideas.
Once the team have exhausted their ideas, they pick one or two of the causes that they believe or have observed happening, which could be causing the issue in question. They then take it to the next stage in the lean route cause analysis model.
5 Whys Analysis
A very simple but powerful tool, the 5 whys simply requires that you become a child again. That means keep asking why…!
Once you have identified where to focus and the potential causes from the Fishbone process, it’s time to investigate further and drill down to find the root causes.
The 5 whys is not strictly based on asking why 5 times – merely, ask it as many times as you need to, until you get to potential root causes.
It’s a simple process. But very powerful.
You’re looking for process fixes, so your answers should all be process fix actions.
Here’s a simple example:
You now need to test your improvement ideas to see if the improvement causes the problem to go away and that what you thought was the root cause actually is.
If it does, standardise the new way of working, so everyone follows it. If not, it’s a case of returning to your Fishbone diagram or 5 whys and finding another cause to drill down on.
Repeating this on many problems will make your teams proficient at getting to route causes. It might sound a lot to do, but it really isn’t. And the more you do, the more effective you’ll become.
Is this the only root cause analysis technique? No, there is no one technique in problem solving and finding root causes. The key is to follow the PDCA framework to find issues, and focus on process fixes. Spend time to observe, check the data and take in the variables that may be causing the problem. When you have a better understanding of the process, identify some ideas and then trial them on a smaller scale to see if they have worked.
Is it as simple as finding one root cause? No, unfortunately, there is not always one root cause. There may be an event where a few conditions cause the problem. You may well have to repeat your experimentation several times until you find the root cause(s) to eliminate the problem you encountered. The point is this scientific way of problem solving works. It requires patience and perseverance.