What is Root Cause Analysis (RCA)?
Root cause analysis (RCA) is the search for the underlying cause of a quality problem. For every problem, there is a cause, and although the term "Root Cause" implies that there is a single cause for a problem, often multiple causes interact and work together to trigger the problem. It is also important to notice there is no single RCA method for all situations; however, the RCA should involve empirical methods and the selection of the appropriate tools for the problem under investigation. An RCA is performed by a root cause investigator; in manufacturing, this could be a quality engineer, quality manager, or even a well-trained production operator.
What aims RCA?
- Identify potential causes.
- Determine which cause or causes are root causes.
- Address those root causes to ensure the effect (the problem) does not recur.
Why is RCA so important?
- If a problem has occurred once, it most likely will occur again (unless something is done to prevent its recurrence.)
- However, if the root cause is found (and it is addressed,) future occurrences of the same problem CAN BE PREVENTED!
- Root cause analysis is the key to preventing future problems.
- Allows learning from past problems, failures, and accidents.
In other words, RCA is a method that helps professionals determine: What happened, How it happened, and Why it happened.
Why is RCA so difficult?
- The problem is poorly defined.
- A systematic approach is not used.
- Investigations are stopped prematurely.
- Decisions are based on guesses, hunches or assumptions.
- An inadequate level of detail is used to get to the real root cause.
- Interim containment fixes are sometimes allowed to become "permanent."
- The skills, knowledge and experience needed to uncover the root cause are not available.
Four keys to successful RCA:
- Use a step-wise approach:
- Standardize the approach throughout the organization.
- Adopt fact-based decision making:
- Don't accept opinions, guesses or hunches.
- Test to confirm:
- If the root cause has been "found," test to confirm you have indeed identified the root cause or causes.
- Implement permanent corrective solutions:
- Does the solution answer the "root cause question?"
- (The root cause question: Does this cause explain all that we know about what the problem is, as well as all we know about what the problem is not?)
- Is the solution practical, feasible and cost-effective?
- Is the solution robust and sustainable?
Root Cause Analysis - Steps
- Identify and clearly define the undesired outcome.
- Gather data.
- Create a timeline.
- Place events & conditions on an event and causal factor tree.
- Use a fault tree or other method/tool to identify all potential causes.
- Decompose system failures down to a basic events or conditions (Further describe what happened)
- Identify specific failure modes (Immediate Causes)
- Continue asking “WHY” to identify root causes.
- Check your logic and your facts. Eliminate items that are not causes or contributing factors.
- Generate solutions that address both proximate causes and root causes.
Can all problems be prevented?
- Probably not - BUT… most recurring problems can be prevented if the root cause is found and addressed.