What is the difference between a Cause Map and a Fault Tree?
by Ely on February 11, 2009
I was recently asked this question following one of my Cause Mapping workshops: what is the difference between a Cause Map and a fault tree? I can understand why this question would be raised, since Cause Mapping and fault tree analysis are both techniques for performing a
root cause analysis. At a fundamental level, all
root cause analysis methods use the same cause-and-effect principle to understand why an incident occurs. The main difference between a Cause Map and a fault tree lies in the focus of the analysis.
A Fault Tree Analysis (also known as a “Probabilistic Risk Assessment”) is focused on the many ways that a failure COULD occur and on the probabilities of each of those failure “branches” occurring. A thorough fault tree analysis is primarily a mathematical model for calculating the probability that each failure branch could occur. This analysis is done in the hope of gaining insight into which areas of the overall system should be improved to increase reliability. The main emphasis is generally on modeling the probability of each branch accurately and a software tool is often needed to construct the mathematical model.
Common Format of a Fault Tree
Cause Maps can also be used to analyze failures that COULD occur, but the focus is generally on building a common understanding of the system and showing the failure modes in a clear manner. I encourage putting colors, diagrams, and evidence on the Cause Map to show how the failure occurs. Of course, if the data is available to assign probabilities to the causes, then this information can also be shown on the Cause Map.
Cause Maps are used extensively for problems that DID occur in the past, because supporting the causes with evidence is crucial to an effective root cause analysis. Fault trees are generally not useful for understanding the cause-and-effect of problems that DID occur, since all of the probabilities are 100% that the causes DID occur. Another important aspect of the Cause Mapping method is that it includes all three steps of effective problem solving: defining the problem, causal analysis, and identifying the best solutions.
-
- Cause Map for a Failed Motor
You must log in to post a comment.