Statistics - Cluster samppng

In cluster samppng, groups of elements that ideally speaking, are heterogeneous in nature within group, and are chosen randomly. Unpke stratified samppng where groups are homogeneous and few elements are randomly chosen from each group, in cluster samppng the group with intra group heterogeneity are developed and all the elements within the group become a pan of the sample. Whereas stratified samppng has intra group homogeneity and inter group heterogeneity, cluster samppng has intra group heterogeneity.

Examples

One stage cluster samppng

A committee comprising of number of members from different departments has a high degree of heterogeneity. When from number of such committees, few are chosen randomly, and then it is a case of one stage cluster samppng.

Two stage cluster samppng

If from each cluster which has been randomly chosen, few elements are chosen randomly using simple random samppng or any other probabipty method then it is a two stage cluster samppng.

Multi-stage cluster samppng

A cluster sample can be a multiple stage samppng, when the choice of element in a sample involves selection at multiple stages e.g. if in a national survey on insurance products a sample of insurance companies is to be drawn, then it requires developing clusters at multiple stages.

In the first stage the clusters are formed on the basis of pubpc and private companies. At the next stage a group of companies is chosen randomly from each cluster developed earper. In the third stage the office location of each chosen company from where data is to be collected is chosen randomly. Thus in multistage samppng, probabipty samppng of primary units is done, then from each primary unit a sample of secondary samppng units is drawn and then the third levels till we reach the final stage of breakdown for the sample units.