Stratified Sampling
A sampling method where the study area is divided into distinct strata (subpopulations) and samples are collected proportionally from each stratum.
Real World
The UK National Vegetation Classification survey divides land into habitat strata (woodland, grassland, heathland) and samples each proportionally, ensuring rare habitats like blanket bog aren't statistically swamped by common grassland.
Exam Focus
When asked to 'evaluate' stratified sampling, always contrast it with random sampling and discuss both proportional allocation and representation of rare strata.
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