Cluster Sampling
The population is divided into clusters, each of which represents a mini-population. A random sample of clusters is selected, and all elements within chosen clusters are observed.Mathematical Idea
Let:- Population divided into \( K \) clusters
- Select \( k \) clusters randomly
$$ \bar{Y} = \frac{1}{k} \sum_{i=1}^{k} \bar{Y}_i $$
where \( \bar{Y}_i \) is the mean of cluster \( i \).
Key Difference from Stratified Sampling
- Stratified sampling: sample from every group
- Cluster sampling: sample entire groups