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# What is Multistage Sampling? (Definition & Example)

Multistage sampling is a method of obtaining a sample from a population by splitting a population into smaller and smaller groups and taking samples of individuals from the smallest resulting groups.

For example, suppose weâ€™re interested in estimating the average household income in the U.S. For simplicity, letâ€™s assume there are 100 million households. This represents the entire population weâ€™re interested in.

However, it would be too expensive and time-consuming to collect income data on each household, so instead we may take a simple random sample of 15 states.

Then, within each state we may take a simple random sample of 10 counties.

Then, within each county we may take a simple random sample of 100 households.

Our resulting sample would contain 15,000 total households:

Sample = 15 states * 10 counties * 100 households = 15,000 households.

This method of obtaining this sample is known asÂ multistage sampling.

In this example there were 3 different stages, but in practice any sampling method that uses two or more stages can be considered multistage sampling.

The important thing is that we use a probability sampling method at each stage â€“ that is, we use a method in which each member of a group is equally likely to be included in the sample.

Examples of probability sampling methods include:

• Simple random sample
• Stratified random sample
• Cluster random sample
• Systematic random sample

You can read details about each of these sampling methods here.

### Examples of Multistage Sampling

Multistage sampling is used in a variety of fields, including:

The Census Bureau: The U.S. Census Bureau uses multistage sampling by first taking a simple random sample of counties in each state, then taking another simple random sample of households in each county and collecting data on those households.

Quality Control: Many warehouses use multistage sampling for assessing quality control. For example, a widget manufacturer may take a simple random sample of packages from a certain production run and then take another simple random sample of widgets from each package to get an estimate of the percentage of defective widgets.

Gallup Polls: Most Gallup polls select a simple random sample of districts in each state and then select a simple random sample of households within each district and collect data on those households.

### Benefits of Multistage Sampling

Multistage sampling offers the following benefits:

• Itâ€™s convenient.
• Itâ€™s generally cost-effective.
• Itâ€™s particularly useful when individuals of interest are geographically dispersed.
• It does not require a complete list of all individuals in a population.

Because of these benefits, it is commonly used in a variety of settings.