Definition

Multistage sampling is a statistical sampling technique that involves dividing a population into multiple stages, with samples being selected at each stage. This method is often used when it is impractical or costly to collect data from the entire population.

Subsampling at Each Stage

In multistage sampling, the population is divided into a series of smaller and more manageable groups or clusters. At each subsequent stage, a sample is selected from the clusters chosen in the previous stage. This process of subsampling is repeated until the final sample, which is usually a representative subset of the entire population.

Primary and Secondary Sampling Units

The initial division of the population into clusters is done using a suitable criterion, such as geographical location or demographic characteristics. These clusters are referred to as primary sampling units (PSUs). Within each PSU, a sample is selected, usually using another sampling method like simple random sampling or stratified sampling. These subsamples are known as secondary sampling units (SSUs).

Benefits of Multistage Sampling

There are several advantages to using multistage sampling:

• Efficiency: Multistage sampling can significantly reduce costs and time compared to other sampling methods, as data collection is spread across stages.
• Manageability: The division of the population into clusters makes the sampling process more manageable, especially with large or geographically dispersed populations.
• Flexibility: Multistage sampling allows for adaptability in selecting samples at each stage, accommodating various sampling techniques depending on the needs of the study.
• Representation: When implemented correctly, multistage sampling can provide accurate and reliable estimates for the entire population by ensuring that diverse clusters are included in the sample.

Usage

Multistage sampling is commonly employed in various fields, such as sociology, market research, epidemiology, and environmental studies. It is particularly useful when the target population is large, spread out, or exhibits a hierarchical structure.