Where does parcel collide?

In psychometrics and structural equation modelling, a parcel is an aggregate of two or more individual items, combined by sum or average, that is then used as a single indicator of a latent construct in place of the separate items. Little, Cunningham, Shahar, and Widaman's To parcel or not to parcel set out when parcelling improves a model's measurement properties and when it hides problems. The referent is a constructed composite indicator built from items, defined by how items are grouped and aggregated, and it has nothing to do with a volume of air or a plot of ground.[1]

Unit

A composite score formed by aggregating a defined set of items

Recovery means

Not applicable

Measured by

Described by the items assigned to it and by the loading and reliability of the resulting composite

In meteorology an air parcel is an imagined small, coherent body of air treated as a unit so its temperature, pressure, and humidity can be tracked as it rises, sinks, and mixes, making it the basic device for reasoning about stability and convection. Wallace and Hobbs's Atmospheric science uses the parcel to derive how a rising volume cools and whether it keeps rising or sinks back. The referent is a conceptual thermodynamic unit of the atmosphere, characterised by its state variables and its buoyancy, a different construct from an aggregate of test items or a surveyed plot of land.[2]

Unit

A notional body of air tracked by its temperature, pressure, and humidity

Recovery means

Not applicable

Measured by

Followed through its thermodynamic state and buoyancy relative to the surrounding environment