stratifier

Stratifier is a term used to denote any agent, device, or criterion that creates stratification, the division of a heterogeneous entity into layers or subgroups called strata. The nature of a stratifier depends on context and can be a statistical variable, a physical sorting mechanism, or a depositional process.

In statistics and survey design, a stratifier is a variable used to partition a population into strata before sampling or analysis. Stratification aims to reduce variance and improve precision. Common stratifiers include geographic region, age group, income bracket, or educational level. The choice of stratifiers affects the efficiency of estimates and may require knowledge of the population.

In physical sciences and industry, stratifiers include separation mechanisms that induce layering by density, particle size, or other properties. Examples are centrifuges that separate components by density, sedimentation that forms strata in soils and sediments, and sorting equipment in mineral processing. In geology and sedimentology, stratification refers to the natural layering of rocks and sediments, produced by depositional processes over time; while not a device, the concept of a stratifier describes processes that generate strata.

The term is not tied to one field with a single formal definition. When encountered, its meaning is determined by context, typically indicating an element that partitions a population or material into strata.