Understanding Sampling Techniques

Many times it is assumed that simple random samples are used by researchers when conducting an experiment. Although the simple random sample is a commonly used technique, there are several other techniques used as well. What are the different types of sampling techniques, and how can we distinguish between these types?

There are five different types of sampling techniques that are commonly used. Those techniques are as follows:

Simple Random

In a simple random sample, "n" objects are selected from a population in such a way that each sample of size "n" is equally liked to be chosen from the population. Also, every member of the population is equally likely to be chosen.

Stratified

in a stratified sample, the population is divided into subgroups called strata. All members of each strata fit a specified trait, such as height, gender, income level, education, and so on. Then random samples are drawn from each strata.

Systematic

In a systematic sample, each member of the population is numbered in order. Then from a specified point, select every so many members to be included in the sample. For example, you can choose to have every 4th, 10th, 15th member, etc, to be part of the sample.

Cluster

In cluster sampling, the population is divided into specific pre-existing groups. Many times these groups are geographic regions. Then, randomly select a group of clusters, and every member from the cluster is part of the sample.

Convenience

In convenience sampling, the sample is chosen by using data from members of the population that are most convenient to use or easiest to obtain.

Here's some examples of the different types of sampling techniques.

Simple random: Assign each teacher in the Wilson School District a number, then select the teachers to be included in the sample using a random number generator.

Stratified: Group sports franchises according to sport: baseball, football, basketball, hockey. Then select a random sample of 12 teams from each sport.

Systematic: Use the Wilson School District faculty directory. Number all of the teachers. Select a starting point in the list of teachers and select every 25th to be included in the sample. Continue selecting members of the sample in this manner until 50 teachers are selected.

Cluster: Divide a state into regions by using the counties. Pick a random sample of 10 counties and include all the businesses in each selected county.

Convenience: Choose 10 newspaper reporters from a local newspaper. Have each reporter select a neighborhood in the area and interview a business owner from any business found. The reporter is finished after interviewing 15 business owners.

This guide should help assist any student having difficulty understanding and distinguishing between the different types of sampling techniques.