Causal factor predefined trees, root cause determination

In general, the companies surveyed use one of two main methodologies to determine root causes. The first involves timeline construction followed by logic tree development. The second involves timeline construction, identification of causal factors, followed by the use of predefined trees or checklists. These two approaches are discussed in detail in Chapter 9. 

Once the causal factors have been identified, the factors are analyzed using a root cause analysis tool, such as 5-AVhys or predefined trees. See Chapter 9 for a more detailed discussion of Barrier Analysis (sometimes called hazard-barrier-target analysis or HBTA) and Change Analysis (also referred to as Change Evaluation/Analysis or CE/A). In essence, these tools act as a filter to limit the number of factors, which are subjected to further analysis to determine root causes. 

The causal factors need to be examined further to determine why those factors existed. The investigation team may use a predefined tree to examine each causal factor individually. The first causal factor is analyzed starting at the top of the tree, and then working down all of the branches as far as the facts permit. When an appropriate subcategory on one of the branches is identified, it is recorded as a root cause. The remaining branches are checked as one causal factor may have multiple root causes. The procedure is then repeated for each causal factor in turn. 

Once the actual incident scenario is understood and its multiple causal factors identified, this information may be used to determine the incident s root causes. One means of performing root cause analysis involves the use of ready-made, predefined trees. A predefined tree provides a systematic approach for analyzing and selecting the relevant elements of the incident scenario. It is a deductive approach, looking backward in time to examine preceding events necessary to produce the specified incident. 

Predefined trees are a convenient means of identifying root causes. Providing all of the causal factors have been determined, use of a comprehensive predefined tree should ensure that most, if not all, root causes are identified. Several quality assurance tests should help identify any remaining root causes. 

A timeline or sequence diagram is first developed, and then causal factors identified. Care should be taken to ensure that the checklist is not used too early. Be sure to determine what happened and how it happened before determining why it happened. Otherwise, the team will think that they have identified the right root cause(s), when in reality only one or two of several multiple causes have been determined. The causal factors are then applied one at a time to each page of the checklist(s) to identify relevant root causes. Those pages that are not relevant to the particular incident of interest are discarded. Similar quality assurance checks should be applied as those described for predefined trees. 

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See also in sourсe #XX -- [ ]

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