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

According to NASA, the following steps must be followed in order to find and solve root causes:
  1. Identify and clearly  define the undesired outcome.
  2. Gather data.
  3. Create a timeline.
  4. Place events & conditions on an event and causal factor tree.
  5. Use a fault tree or other method/tool to identify all potential causes.
  6. Decompose system failures down to a basic events or conditions  (Further describe what happened)
  7. Identify specific failure modes (Immediate Causes)
  8. Continue asking “WHY” to identify root causes.
  9. Check your logic and your facts.  Eliminate items that are not causes or contributing factors.
  10. 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.