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CADDIS Volume 1: Stressor Identification

Step 5: Identify Probable Causes

Step 5—identifying the probable cause—is the last step in the Stressor Identification (SI) process. Based on available evidence organized in Steps 3 and 4, you will distinguish the most probable cause(s) from a set of less probable causes. This is why several candidate causes are listed at the beginning of the causal analysis process. Ultimately the case for a candidate cause must be evaluated as a consistent and credible argument. Then, each candidate cause must be compared to every other candidate cause to determine which causes led to the specific effects. Your rationale for identifying one cause relative to the others needs to be clear, reasonable, and convincing if management action is to be motivated and effectively directed. The consequences of deferring a decision versus making an incorrect decision need to be considered carefully.

Your analysis leads to the final position statement of the causal assessment. Therefore, it is most important that this step be undertaken with knowledge, evenness, and care. It helps to be aware of what is known and what is not known. In particular the quality of the data and the causal analysis should be included in the description of the determination of the most probable cause. Sometimes it helps to record what additional information would significantly strengthen the determination. Above all, remain objective and question assumptions, biases, and motives at every opportunity. Sometimes it helps to record unstated assumptions that you have made.

Determining the most probable causal agent from several candidates requires that you somehow retain and convey a lot of information, especially the most compelling lines of evidence. These can be recorded on tables of evidence or on annotated conceptual models. It is a good idea for the investigator to review the documentation of the measurements that underlie the causal association, that is, the evidence. You need to be comfortable with the information. If you are unfamiliar with a particular discipline, consult a specialist in that area.

This step is divided into two tasks to make the process of determining a probable cause more manageable. In the first task, the evidence for each candidate cause is evaluated, candidate causes are sorted into categories, and the most compelling lines of evidence are noted. In the second task, the evidence for candidate causes is compared across all candidate causes. The product is the identification of the candidate cause or causes for the biological impairment and a description of the evidence for that decision.

In the best case, a probable cause or causes are identified, and the information is effectively communicated to managers and stakeholders. In some situations, no cause is identified or the confidence in conclusions will be too low to support management action. However, even when this happens, by going through this process you will likely be able to make a strong recommendation for the collection of additional information that will enable a cause to be identified.

The output of Step 5 should include the following elements:

  • Scores for each type of evidence displayed in a table,
  • An evaluation of the consistency and credibility of the case based on the scores,
  • A classification of each candidate cause as refuted, diagnosed, probable, unlikely or uncertain,
  • A discussion of the reasons for the final conclusions including the most compelling lines of evidence, and
  • A report describing the causal assessment.

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