Instances of the class [Observation](https://schema.org/Observation) are used to specify observations about an entity at a particular time. The principal properties of an [Observation](https://schema.org/Observation) are [observationAbout](https://schema.org/observationAbout), [measuredProperty](https://schema.org/measuredProperty), [statType](https://schema.org/statType), \[\[value\] and [observationDate](https://schema.org/observationDate) and [measuredProperty](https://schema.org/measuredProperty). Some but not all Observations represent a [QuantitativeValue](https://schema.org/QuantitativeValue). Quantitative observations can be about a [StatisticalVariable](https://schema.org/StatisticalVariable), which is an abstract specification about which we can make observations that are grounded at a particular location and time. Observations can also encode a subset of simple RDF-like statements (its observationAbout, a StatisticalVariable, defining the measuredPoperty; its observationAbout property indicating the entity the statement is about, and [value](https://schema.org/value) ) In the context of a quantitative knowledge graph, typical properties could include [measuredProperty](https://schema.org/measuredProperty), [observationAbout](https://schema.org/observationAbout), [observationDate](https://schema.org/observationDate), [value](https://schema.org/value), [unitCode](https://schema.org/unitCode), [unitText](https://schema.org/unitText), [measurementMethod](https://schema.org/measurementMethod).