CQFM Population Basis

The population basis specifies the type of elements in the population. For a subject-based measure, this is boolean (because the subject and the population basis are the same, and the population criteria define yes/no values for each individual in the population). For measures that have a population basis that is different than the subject, this element specifies the type of the population basis. For example, an encounter-based measure has a subject of Patient and a population basis of Encounter, and the population criteria all return lists of Encounters. Note that the subject of a measure can be found in the element [subject[x].](https://hl7.org/fhir/us/cqfmeasures/StructureDefinition-computable-measure-cqfm-definitions.html#Measure.subject[x])