description: 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. package_name: hl7.fhir.us.cqfmeasures derivation: constraint name: CQFMPopulationBasis type: Extension elements: url: type: uri pattern: {type: Uri, value: 'http://hl7.org/fhir/us/cqfmeasures/StructureDefinition/cqfm-populationBasis'} index: 0 value: choices: [valueCode] index: 2 valueCode: {type: code, choiceOf: value, index: 3} package_version: 5.0.0-ballot class: extension kind: complex-type url: http://hl7.org/fhir/us/cqfmeasures/StructureDefinition/cqfm-populationBasis base: http://hl7.org/fhir/StructureDefinition/Extension version: 5.0.0-ballot