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Governance, Risk, Audit & Privacy · Advanced

Stratified Sampling

Dividing a population into homogeneous subgroups (strata) and sampling from each.

Definition

Stratification improves efficiency and precision when populations have high variability, for example by grouping transactions by dollar amount. High-value strata may be tested 100 percent.

Example

All payments over $100,000 are tested, while smaller payments are randomly sampled.

Exam tip

Stratification reduces sample size needed for a given precision in variable populations.

Related terms