# populationType

Indicates the populationType common to all members of a [StatisticalPopulation](https://schema.org.ai/StatisticalPopulation) or all cases within the scope of a [StatisticalVariable](https://schema.org.ai/StatisticalVariable).

## Expected Types

| Type | Description |
|------|-------------|
| [Class](https://schema.org.ai/Class) | A class, also often called a 'Type'; equivalent to rdfs:Class. |

## Used on Types

| Type | Description |
|------|-------------|
| [StatisticalPopulation](https://schema.org.ai/StatisticalPopulation) | A StatisticalPopulation is a set of instances of a certain given type that satisfy some set of constraints. The property [populationType](https://schema.org.ai/populationType) is used to specify the type. Any property that can be used on instances of that type can appear on the statistical population. For example, a [StatisticalPopulation](https://schema.org.ai/StatisticalPopulation) representing all [Persons](https://schema.org.ai/Person) with a [homeLocation](https://schema.org.ai/homeLocation) of East Podunk California would be described by applying the appropriate [homeLocation](https://schema.org.ai/homeLocation) and [populationType](https://schema.org.ai/populationType) properties to a [StatisticalPopulation](https://schema.org.ai/StatisticalPopulation) item that stands for that set of people. The properties [numConstraints](https://schema.org.ai/numConstraints) and [constraintProperty](https://schema.org.ai/constraintProperty) are used to specify which of the populations properties are used to specify the population. Note that the sense of "population" used here is the general sense of a statistical population, and does not imply that the population consists of people. For example, a [populationType](https://schema.org.ai/populationType) of [Event](https://schema.org.ai/Event) or [NewsArticle](https://schema.org.ai/NewsArticle) could be used. See also [Observation](https://schema.org.ai/Observation), where a [populationType](https://schema.org.ai/populationType) such as [Person](https://schema.org.ai/Person) or [Event](https://schema.org.ai/Event) can be indicated directly. In most cases it may be better to use [StatisticalVariable](https://schema.org.ai/StatisticalVariable) instead of [StatisticalPopulation](https://schema.org.ai/StatisticalPopulation). |
| [StatisticalVariable](https://schema.org.ai/StatisticalVariable) | [StatisticalVariable](https://schema.org.ai/StatisticalVariable) represents any type of statistical metric that can be measured at a place and time. The usage pattern for [StatisticalVariable](https://schema.org.ai/StatisticalVariable) is typically expressed using [Observation](https://schema.org.ai/Observation) with an explicit [populationType](https://schema.org.ai/populationType), which is a type, typically drawn from Schema.org. Each [StatisticalVariable](https://schema.org.ai/StatisticalVariable) is marked as a [ConstraintNode](https://schema.org.ai/ConstraintNode), meaning that some properties (those listed using [constraintProperty](https://schema.org.ai/constraintProperty)) serve in this setting solely to define the statistical variable rather than literally describe a specific person, place or thing. For example, a [StatisticalVariable](https://schema.org.ai/StatisticalVariable) Median\_Height\_Person\_Female representing the median height of women, could be written as follows: the population type is [Person](https://schema.org.ai/Person); the measuredProperty [height](https://schema.org.ai/height); the [statType](https://schema.org.ai/statType) [median](https://schema.org.ai/median); the [gender](https://schema.org.ai/gender) [Female](https://schema.org.ai/Female). It is important to note that there are many kinds of scientific quantitative observation which are not fully, perfectly or unambiguously described following this pattern, or with solely Schema.org terminology. The approach taken here is designed to allow partial, incremental or minimal description of [StatisticalVariables](https://schema.org.ai/StatisticalVariable), and the use of detailed sets of entity and property IDs from external repositories. The [measurementMethod](https://schema.org.ai/measurementMethod), [unitCode](https://schema.org.ai/unitCode) and [unitText](https://schema.org.ai/unitText) properties can also be used to clarify the specific nature and notation of an observed measurement. |

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Quoted from Schema.org 30.1, https://schema.org/populationType, under CC BY-SA 3.0. Served by the Org.AI Foundation at https://schema.org.ai/populationType.