Root Cause Analysis (RCA) is a problem-solving methodology that steps you through the RCA process. Each RCA process phase has a range of root cause analysis tools that you can use.
The RCA process starts at the problem event then moves through evidence collection, investigation, analysis, developing corrective actions to address the problem or a failure, and concludes with the RCA Report.
Figure below shows the basic RCA process and the root cause analysis tools you can use in each step.
There are more advanced, highly technical RCA tools too, but the ones bullet pointed in the Figure are the foundational tools that can be applied in every RCA.
Each methodology deserves to be thoroughly understood by those putting them to use. Here are summarized the most helpful tools you can use for RCA:
1. Fault Tree Analysis (FTA)
This is a deductive procedure used to determine the various combinations of hardware and software failures and human errors that could cause undesired events (referred to as top events) at the system level.
FTA relies on multiple expert opinions and judgements at various stages and provides a common perspective on a given problem.
Recommended Applications:
- Analyzing and forecasting system reliability, maintainability, and safety
- Understanding the logic leading to a “top event” or undesired state
- Demonstrating compliance with system safety and reliability requirements
- Prioritizing multiple contributors which led to a top event or undesired state
2. Fishbone Diagram
Fishbone Diagram also called a cause and effect or Ishikawa diagram, a fishbone diagram is a visual tool for looking at cause and effect.
A problem or effect is displayed at the the “head” or “mouth” of the fish and possible contributing factors are listed on the “bones” under various cause categories.
These models work best when the “head” of the fish contains a very detailed problem statement.
Recommended Applications:
- Directing a team to focus on identifying all possible categories and consider alternative causes
- Refocusing a team on the causes of a problem rather than the symptoms
- Improving product design
- Preventing quality defects
- Identifying potential factors causing an overall effect
3. 5 Whys
The 5 Whys is arguably the simplest technique for root cause analysis.
It can be very effective when answers come from people who have hands-on experience in the process being examined.
Recommended Applications:
- Resolving simple or moderately difficult problems
- Resolving issues involving human factors
- Resolving issues where statistical analysis is not needed or possible
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