Definition

Noun: A stratified sample is a type of statistical sample where the entire population is first divided into distinct, non-overlapping subgroups called strata. A random sample is then independently taken from each of these strata. This method ensures representation from all key subgroups within the population.

Usage

This term is used in the context of statistics, research methodology, and data analysis. It describes a specific sampling technique designed to improve accuracy and reduce sampling bias by guaranteeing that subgroups (strata) of interest are adequately represented in the final sample.

Examples

• To ensure all age groups were represented, the researchers used a stratified sample, drawing participants separately from the 18-25, 26-40, and 41-60 age brackets.
• The poll's accuracy was attributed to its stratified sample, which proportionally represented urban, suburban, and rural voters.
• When studying employee satisfaction, a stratified sample can be taken from each department to get a complete picture of the organization.

Advanced Usage

• Proportionate vs. Disproportionate Stratified Sampling: In a , the size of the sample from each stratum is proportional to the stratum's size in the population. In a , the sample sizes are not proportional, often to ensure sufficient data is collected from smaller, important subgroups.
• Stratified Random Sampling: This is the full name of the technique, emphasizing that the sampling within each stratum is random.

Variants and Related Words

• Stratify (verb): To arrange or classify into strata.
  • The data was stratified by income level before analysis.
• Stratification (noun): The process of forming strata or the state of being arranged in strata.
  • Social stratification was a key factor in the study's design.
• Stratum (noun, plural: strata): One of the subgroups or layers into which a population is divided.
  • Each stratum was sampled independently.

Synonyms

• Stratified random sample
• Representative sample (when properly stratified to reflect the population structure)

Related Terms and Concepts

• Random Sample: A sample where every member of the population has an equal chance of being selected. Stratified sampling uses random sampling within each stratum.
• Cluster Sample: A different sampling method where the population is divided into clusters, and a random sample of is chosen, after which all members within the chosen clusters are studied.
• Sampling Bias: A flaw in sample selection that causes some members of the population to be less likely to be included than others. Stratified sampling aims to minimize this.

Noun

1. the population is divided into strata and a random sample is taken from each stratum