Why–because analysis (WBA) is a method for
accident analysis
Accident analysis is a process 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 in ...
using
graph theory
In mathematics and computer science, graph theory is the study of ''graph (discrete mathematics), graphs'', which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of ''Vertex (graph ...
.
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
('from the earlier') and ('from the later') are Latin phrases used in philosophy to distinguish types of knowledge, justification, or argument by their reliance on experience. knowledge is independent from any experience. Examples include ...
) analysis method. Application of WBA aims to ensure objectivity,
falsifiability
Falsifiability (or refutability) is a deductive standard of evaluation of scientific theories and hypotheses, introduced by the Philosophy of science, philosopher of science Karl Popper in his book ''The Logic of Scientific Discovery'' (1934). ...
and reproducibility of results.
The result of a WBA is a why–because graph (WBG), which is a type of
causal notation
Causal notation is notation used to express cause and effect.
In nature and human societies, many phenomena have causal relationships where one phenomenon A (a cause) impacts another phenomenon B (an effect). Establishing causal relationships i ...
used to represent interdependencies within a system. The WBG depicts
causal relations 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 ...
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 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
*
Accident
An accident is an unintended, normally unwanted event that was not deliberately caused by humans. The term ''accident'' implies that the event may have been caused by Risk assessment, unrecognized or unaddressed risks. Many researchers, insurers ...
*
Cause–effect graph
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Fault tree analysis
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Five whys
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Ishikawa diagram
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Issue map
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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
Problem solving methods