Often, when a new problem arises and needs to be solved, I quickly think of a solution. Later, I realize that maybe that was not the best solution. Has this ever happened to you? It’s a natural tendency. We want to solve our problems as quickly as possible, without taking the time to analyze their causes properly. This is precisely the topic of this post: cause analysis.
We tend to be blind to some causes that seem obvious to other people. Since we don’t see them, we don’t analyze them, so the solutions we generally apply are only patches that only hide the real cause of the problem for a time. The problem then reappears and we continue to waste time and money in a futile attempt to solve it.
What is a root cause analysis?
A root cause is the main cause that gave rise to the problem. Problems appear when we have variations in normal systems or procedures, so, to solve these problems, we need to look for the causes.
As I was saying, we could just look for the first cause that comes to mind. Or, we can train our teams to conduct a detailed cause-and-effect analysis every time a problem arises to make sure we always solve it the first time around.
Types of root causes
Common or environmental causes
These usually cover 85% of cases. They are called common causes because they also affect everyone who is exposed to the same conditions. Poor lighting, humidity, vibration, lack of an adequate quality program, poor supervision or instructions, problematic procedures and incompatibility between requirements and results are all examples of common or environmental causes.
These are failures in the system, so they usually continue until they are addressed by management. Employees can’t change the lighting, write new contracts for raw materials or demand high-level actions.
Special or local causes
These are specific causes arising from local conditions, so they are easier to detect and, in many cases, can be corrected by the employees themselves.
Common causes are harder to identify than special causes. When all the special causes have been eliminated, the common causes remain. Once a common cause is identified, management has to decide whether it is economically viable to address it. Management’s obligation is to focus on the common causes that produce variability, but in many companies, employees are the first to get the blame, even though only 15% of causes are under the responsibility of employees.
However, if we really want to get rid of quality problems, root cause analysis must be carried out to identify the real causes and determine whether they are common (to be addressed by management) or special (to be addressed by employees).
Tools for identifying causes
It is always recommended to work in teams to solve problems, asking experts, managers and operators (depending on the severity of the problem) to participate to ensure that you get ideas from everyone involved.
These are three tools that will help you to put together all the ideas, organize them and give you a clear view of the causes of the problem.
1. The 5 Whys
To identify the root cause of a problem, Taiichi Ohno of Toyota asked workers to ask “why?” five times. Frame the problem as a question, ask “why?”, write down each of the causes and, for each cause, keep asking “why?” until no more answers can be obtained. By the time you’ve asked “why?” five times, you’re usually at the root cause. Use the suggested final causes to generate possible solutions and use data to accept or reject each proposed cause.
2. Fishbone Diagram (or Ishikawa Diagram)
This diagram breaks down a problem into potential logical causes in a visual manner. You can use the Ishikawa diagram to detail each main cause to be certain you arrive at the root cause. Your team can use complementary techniques (like polls) to restrict the list and test the chosen option. This technique is effective and simple.
3. Fault tree analysis (FTA)
This is a top-down deductive analysis. It starts with a top event that poses a risk, and moves down, layer by layer, repeating the same question until the root causes are identified. The basic question when doing a fault tree analysis is “which faults can cause risk?”
After detecting that you have a problem, you can use the 5 Whys or Ishikawa diagrams to understand why this occurred. Common causes generate more branches in your diagrams, but special causes will be clear enough that any employee can detect them alone.
Root cause analysis was developed to help identify not only what event occurred and how, but also why it happened. Understanding why an event occurred is critical for developing effective solutions, and identifying the root causes is the key to avoiding similar recurrences.