What is a Hypothesis?

By definition, a hypothesis is a tentative assumption intended to explain certain facts or observations. Within the context of an RCA Analysis, a hypothesis represents a theory about the root cause of a failure event.

In the Logic Tree, a hypothesis is represented by a Hypothesis node, which is defined in an associated RCA Hypothesis record. Hypothesis nodes can appear below Failure Mode nodes and other Hypothesis nodes in the Logic Tree. When you add a Hypothesis node to the Logic Tree, a link is created between the RCA Hypothesis record and the RCA Analysis record. A link is also created between the RCA Hypothesis record and either the RCA Failure Mode record or the predecessor RCA Hypothesis record.

The following image shows an example of a completed RCA Hypothesis datasheet.

The RCA Hypothesis datasheet contains the following fields:

  1. Label: A description of the hypothesis as you want it to appear on the Logic Tree.  

  2. Description: A detailed description of the hypothesis.

  3. Confidence Factor: A value that indicates the probability that the hypothesis is true. The list contains values that range from Not True (0) to True (5). You can choose ONE of the six values. If you select a value in this field, the value that you select will appear in brackets to the right of the hypothesis name in the Logic Tree.

Note: For more information on Hypothesis node states, see the Hypothesis States section of this Help system.

The following image shows an example of how a Hypothesis node and the associated RCA Hypothesis record will look in the Logic Tree when it is first created.


To the right of the label that you assign to the Hypothesis node, a number appears, indicating the level of confidence that the team has in the hypothesis being true. After a given RCA Hypothesis record has been created, the team can create an RCA Verification record to test the hypothesis. The team will then change the state of the RCA Hypothesis record according to the results of the RCA Verification record.

You can define multiple Hypothesis nodes for any RCA Failure Mode record or RCA Hypothesis record, meaning that one cause could have been caused by something else. For example, a lubrication issue may cause a cooling water pump to overheat, but that lubrication issue was caused by an operator who did not apply enough lubricant, which was caused by inadequate accountability of workers. In this case, the lubrication issue is a physical cause, too little lubrication applied is a human cause, and the latent root cause is the inadequate accountability of workers. The following image shows how this scenario would appear in the Logic Tree.