Update likelihood criteria for rating observations

Why is this change being made?

When initially creating observations I was having challenges risk rating specifically determining the likelihood score. Reviewed NIST 800-30 and determined that frequency of identifying/having a control observation is not a criteria that is used to determine likelihood. Based on my understanding the risk of occurrence (likelihood) and lack of a control operating effectively are two separate situations.

As an example, when I assessed a lower tiered system last quarter a control did not exist to perform backup restores. The risk of not having a back up restore is lack of availability of data; however, there was a control to ensure backups were being performed. Based on our previous likelihood criteria, the absence of a control or control observations persisting would rate the risk as high likelihood which would inherently inflate the risk rating. I believe context matters when risk rating and shouldn't use control observation as a criteria to determine likelihood.

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