As a data steward I need to know what the quality thresholds are for my quality type policies and the rules associated.  I can document these as sigma levels are pure passing or defect percentage.  This allows me to differentiate between critical data elements (CDEs) that may have a higher threshold then less critical data elements.  Allows allows me to tell if the current data quality score is passing or failing based on standards associated to this.

i.e. A Policy of type standard would be made to ensure that all Critical Data Elements had a threshold of no less than 4 Sigma.  That could then be applied to this attribute as a default for rules associated to thresholds identified as CDEs.