Root cause analysis (RCA) is a practical problem-solving tool. Once a root cause found we can concentrate on the solution that is related to the found root cause.
A definition of a Root Cause is extremely important for the problem-solving process. We should clearly define and understand what a Root Cause is. Otherwise, RCA becomes completely useless, besides a problem will not be solved.
Everyone remembers a traditional definition:
ROOT CAUSE IS A FUNDAMENTAL REASON FOR THE OCCURRENCE OF THE PROBLEM.
This definition is very popular and clear, but we have to take into account the limitations that such definition affords. The definition apriori forces us into the one and only option to solve the problem by removing the Fundamental Reason of the Problem – Fundamental Root Cause (FRC).
It is important to mention that, in most cases, real FRC typically cannot be changed and does not help us to solve the existing problem.
Nevertheless, if the FRC removed than it is most probable that the problem will not occur again in the future.
Therefore the second definition is created:
ROOT CAUSE IS A AUXILIARY REASON FOR THE OCCURRENCE OF THE PROBLEM THAT IF REMOVED THE PROBLEM DISAPPEARES.
Such a definition of the Root Cause is much more useful and practical because it actually directs us to solve the problem. On the other hand, a fundamental reason for the problem will remain unchanged hence the problem will occur again in the future.
The difference between the two types of root causes is described in the chart below:
A problem always have both FRC and ARC
Cause and Effect Chain (CEC) Analysis is the most popular instrument for a root cause search. We have already touched on this aspect in one of our previous blogs: A problem solver is the main roadblock in problem-solving processes.
The CEC analysis is based on a very simple idea:
Nothing happens without a reason.
The purpose of the tool is to find a root cause, create new ideas, and find the best solution to a problem.
CEC tool requires to create a logical chain answering the question “Why?” moving from “Target Problem” link by link down to a “Key Problem.”
“Target Problem” – a problem statement.
“Key Problem” – is a logical end of the chain – a dead end of the chain.
A typical result of the CEC analysis is a flow diagram having ramified branches as shown below:
From our experience, people rarely get to the fundamental reason for the problem, instead, they interrupt the analysis at the reason that seems to be excellent, best and effective to be addressed. Being under Psychological Inertia people typically stop analyzing each branch at the reason that they are familiar and feel comfortable with.
Such an approach produces results but limits the amount of possible ARC’s hence limits the number of possible solutions.
We want to offer you several tips which we established based on our expertise in problem-solving in science and industry.
Typical CEC ramified diagram is shown in Fig. 1. Such an illustration of the CEC sequence seems impressive but does not really help in a Root Cause search.
Use regular linear chains without a ramification. Instead of analyzing the ramified structure, split the tree into separated linear chains. Each linear chain should be created and analyzed separately.
As an example, the tree shown in Fig. 1 should be presented as three linear chains, as shown in Fig. 2 below.
Do not waste time looking at ramified CEC tree, work with linear chains.
Create a CEC using the smallest possible links of the chain. This is a way to analyze as many reasons as possible and not to lose potential candidates for solutions. Analyze the problem by slicing it in very fine steps as if you slicing bread into very thin pieces searching for very small pearl pea that was born within the bread.
While answering the question “Why?” do not stop until the logical end (dead end) of the chain is achieved. The dead-end should be something that is not fixable or changeable in the current situation. For instance, “because the density of plastic is lower than that of iron”, “because the tolerance of the robot performance is not tight enough”, “because the electrical conductivity of copper is higher than that of tantalum” and so on. Achieving the dead-end ensures that all possible reasons found and mentioned within the CEC you created.
People are typically looking for the end of the chain as the root cause and that is incorrect.
There are two types of Root Cause:
Type one root cause is the end of the chain and that is Fundamental reason for the occurrence of the problem – Fundamental Root Cause (FRC). FRC brings us to the solution that typically does not help to solve the current problem, but if this Root Cause is removed, the problem will not take place in the future.
Type two root cause is Auxiliary Root Cause (ARC) that is the intermediate reason for the current problem, but if removed the problem decreases. However, it will not prevent the problem to occur in the future.
Keep in mind, the elimination of any link in the CEC solves the target problem.
Remember, any of the ARC could be designated as an actual root cause. The existing problem can be solved by elimination of the chosen root cause. Therefore the sequence of root cause analysis should be as follows.
Hence, the attribute of the CEC end (dead-end) is that it is unchangeable or somehow used for the solution of the current problem.
All the rest of the causes are ARC’s which can and should be used for the solution of the current problem.
Below is an example of both cases:
ARC elimination solves the current problem, but the problem may return
FRC elimination does not solve the current problem but prevents it from occurring in the future
Headache is a problem. Let’s perform the Root cause Search: first, Cause-Effect Chain Analysis and second, Root Cause Analysis.
Below is the Cause-Effect Chain Analysis:
In conclusion, the CEC is completed because of the last-mentioned reason is unchangeable. Even if fixed the “headache” problem may not occur in the future, but the problem currently will not be solved. This is a Fundamental Reason for the Problem.
Now we can start Root Cause Analysis moving from the bottom of the chain to the top.
Below is the result of the analysis:
As a matter of fact, the bottom Cause is the dead-end of the chain. It is FRC. We can try to remove it by special advertising, changing the laws and regulations, we can also initiate the production of special drugs preventing pregnant women from smoking or reducing the circumstances of smoking. This generally could reduce the harmful effect in the future, but will never reduce my pain.
Subsequently, all the rest of the Root Causes are ARC’s. Eliminating any of them may solve the current problem, but will not prevent it from occurring in the future.
The best way is to reveal all possible solutions, compare them and choose the most suitable one. Our Round – Robin Ranking (RRR) is the best tool for such a ranking job.
We discussed it in our blog Round Robin Ranking (RRR) is a practical problem-solving tool.
Now get into our Innovation Platform and use our new Cause and Effect Chain tool. Cause-Effect Chain Analysis, Root Cause Analysis, and Ranking of possible solutions are smoothly integrated into the platform.
LOGIN to PRIZ Innovation Platform and start your project.
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