Why–because analysis (WBA) is a method for
accident analysis
Accident analysis is carried out in order to determine the cause or causes of an accident (that can result in single or multiple outcomes) so as to prevent further accidents of a similar kind. It is part of ''accident investigation or incident in ...
.
It is independent of application domain and has been used to analyse, among others, aviation-, railway-, marine-, and computer-related accidents and incidents. It is mainly used as an after-the-fact (or
a posteriori) analysis method. WBA strives to ensure objectivity,
falsifiability
Falsifiability is a standard of evaluation of scientific theories and hypotheses that was introduced by the philosopher of science Karl Popper in his book '' The Logic of Scientific Discovery'' (1934). He proposed it as the cornerstone of a s ...
and reproducibility of results.
The result of a WBA is a why–because graph (WBG). The WBG depicts
causal relation
In mathematical physics, the causal structure of a Lorentzian manifold describes the causal relationships between points in the manifold.
Introduction
In modern physics (especially general relativity) spacetime is represented by a Lorentzian m ...
s between factors of an accident. It is a
directed acyclic graph
In mathematics, particularly graph theory, and computer science, a directed acyclic graph (DAG) is a directed graph with no directed cycles. That is, it consists of vertices and edges (also called ''arcs''), with each edge directed from one v ...
where the nodes of the graph are factors. Directed edges denote
cause–effect relations between the factors.
WBA in detail
WBA starts with the question "What is the accident or accidents in question?". In most cases this is easy to define. Next comes an iterative process to determine causes. When causes for the accident have been identified, formal tests are applied to all potential cause-effect relations. This process can be iterated for the newfound causes, and so on, until a satisfactory result has been achieved.
At each node (factor), each contributing cause (related factor) must have been
necessary to cause the accident, and the totality of causes must have been
sufficient
In logic and mathematics, necessity and sufficiency are terms used to describe a conditional or implicational relationship between two statements. For example, in the conditional statement: "If then ", is necessary for , because the truth of ...
to do so.
The formal tests
The ''counterfactual test'' (CT) – The CT leads back to
David Lewis' formal notion of causality and
counterfactuals. The CT asks the following question: "If the cause had not been, could the effect have happened?". The CT proves or disproves that a cause is a necessary causal factor for an effect. Only if it is necessary for the cause in question then it is clearly contributing to the effect.
The ''causal sufficiency test'' – The CST asks the question: "Will an effect always happen if all attributed causes happen?". The CST aims at deciding whether a set of causes are sufficient for an effect to happen. The missing of causes can thus be identified.
Only if for all causal relations the CT is positive and for all sets of causes to their effects the CST is positive the WBG is correct: each cause must be necessary (CT), and the totality of causes must be sufficient (CST): nothing is omitted (CST: the listed causes are sufficient), and nothing is superfluous (CT: each cause is necessary).
Example
See also
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Accident
An accident is an unintended, normally unwanted event that was not directly caused by humans. The term ''accident'' implies that nobody should be blamed, but the event may have been caused by unrecognized or unaddressed risks. Most researche ...
*
Cause–effect graph
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Fault tree analysis
Fault tree analysis (FTA) is a type of failure analysis in which an undesired state of a system is examined. This analysis method is mainly used in safety engineering and reliability engineering to understand how systems can fail, to identify ...
*
Five whys
Five whys (or 5 whys) is an iterative interrogative technique used to explore the cause-and-effect relationships underlying a particular problem. The primary goal of the technique is to determine the root cause of a defect or problem by repeating ...
*
Ishikawa diagram
Ishikawa diagrams (also called fishbone diagrams, herringbone diagrams, cause-and-effect diagrams) are causal diagrams created by Kaoru Ishikawa that show the potential causes of a specific event.
Common uses of the Ishikawa diagram are product ...
*
Issue map
The issue-based information system (IBIS) is an argumentation-based approach to clarifying wicked problems—complex, ill-defined problems that involve multiple stakeholders. Diagrammatic visualization using IBIS notation is often called issue ...
*
Issue tree
An issue tree, also called logic tree, is a graphical breakdown of a question that dissects it into its different components vertically and that progresses into details as it reads to the right.
Issue trees are useful in problem solving to ide ...
*
Root cause analysis
In science and engineering, root cause analysis (RCA) is a method of problem solving used for identifying the root causes of faults or problems. It is widely used in IT operations, manufacturing, telecommunications, industrial process control ...
References
External links
Why-Because Analysis(WBA)
{{DEFAULTSORT:Why-because analysis
Causal diagrams
Debugging
Accident analysis
Directed graphs