Tasoryhmien

Tasoryhmien is a Finnish term used in statistics and social sciences to refer to strata or level groups within a population. The concept describes dividing a population into non-overlapping subgroups, or strata, that are internally similar regarding a chosen characteristic (for example age, income, or region) while differing between strata. The full set of strata partitions the population and each individual belongs to exactly one group. The purpose of forming tasoryhmien is to increase the efficiency and precision of estimates in surveys and to enable targeted analysis within homogeneous subpopulations.

In practice, strata can be defined before data collection (pre-stratification) or adjusted after data collection (post-stratification). Sample sizes may be allocated to strata proportionally to their size or by optimal allocation to minimize variance under cost constraints. Applications include stratified sampling, where samples drawn from each stratum are combined to form an overall estimate, and analyses that require comparisons among different levels, such as age or income brackets. Tasoryhmien are also used in education assessment, market research, and public health to tailor interpretations and interventions to specific subpopulations.

Related concepts include stratified sampling, weighting, quota sampling, and multistage sampling. The term reflects Finnish linguistic roots from taso (level) and ryhmä (group), and is commonly encountered in Finnish-language statistical literature.