Definition

Noun: A method of sampling where the entire population is first divided into distinct, non-overlapping subgroups (called strata) based on shared characteristics or attributes (e.g., age, income, location). Simple random samples are then independently drawn from each of these strata.

Usage

This term is used primarily in the context of statistics, research methodology, and data analysis. It describes a specific technique for selecting a sample that is representative of the entire population by ensuring all key subgroups are proportionally included.

Examples

• Basic Usage:
  • To ensure all age groups were represented, the researchers used stratified sampling, creating strata for 18-30, 31-50, and 51+ year-olds.
  • The accuracy of the poll was improved by employing stratified sampling based on voter registration district.
• In Academic/Technical Writing:
  • The study utilized stratified sampling to guarantee proportional representation from urban, suburban, and rural strata.
  • Stratified sampling reduces sampling error when the strata are homogeneous internally but different from each other.

Advanced Usage

• Proportionate vs. Disproportionate Stratified Sampling: Within the main method, a key distinction exists.
  • Proportionate stratified sampling involves selecting sample sizes from each stratum that are proportional to the stratum's size in the overall population.
  • Disproportionate (or optimal) stratified sampling involves intentionally varying the sampling fraction across strata, often to oversample a small but important subgroup to ensure it has enough data points for analysis.

Variants and Related Words

• Stratify (verb): To arrange or classify into strata.
  • The data was stratified by income level before analysis.
• Stratum (noun, plural: strata): One of the subgroups or layers into which a population is divided.
  • Each stratum was sampled randomly.
• Stratification (noun): The process of dividing into strata.
  • The stratification of the sample was based on geographic region.

Synonyms

• Stratified random sampling
• Stratum sampling

Related Terms and Concepts (Not Synonyms)

• Simple Random Sampling: A basic sampling method where every member of the population has an equal chance of being selected, without prior stratification.
• Cluster Sampling: A method where the population is divided into clusters (often geographically), a random sample of clusters is chosen, and all members within the chosen clusters are surveyed.
• Sampling Frame: The actual list or source from which a sample is drawn.
• Representative Sample: A sample that accurately reflects the characteristics of the population it is intended to represent; stratified sampling is a technique to achieve this.

Noun

1. the population is divided into subpopulations (strata) and random samples are taken of each stratum