What Is Difference Between Stratified Sampling And Clustered Sampling?

If the population is not homogeneous or heterogeneous with respect to a variable, then the population is divided into sub-groups known as strata. A stratum is a homogeneous group with respect to variables. If we have to select a sample from the population, then the sample is selected from these strata. This sampling is known as stratified random sampling.

A cluster is a collection of units found in nature. In cluster sampling we first select at random clusters of individual items to make up the over all samples. Clusters are called as primary sampling units. If all the units of the selected clusters are included in the sample, it is called single stage-cluster sampling.