Criteria for specifying the entities to be evaluated by a specific quality measure, based on a shared common set of characteristics (within a specific measurement set to which a given measure belongs). The denominator can be the same as the initial population, or it may be a subset of the initial population to further constrain it for the purpose of the eMeasure. Different measures within an eMeasure set may have different denominators. Continuous Variable eMeasures do not have a denominator, but instead define a measure population.

It can be the same as the initial patient population or a subset of the initial patient population to further constrain the population for the purpose of the eMeasure. Different measures within an eMeasure set may have different Denominators. Continuous Variable eMeasures do not have a Denominator, but instead define a Measure Population.