What are the different methods of survey sampling?
Determining your sample, or the group of people participating in your survey, is one of the most crucial steps of conducting it.
There are two main kinds of sampling techniques — probability and non-probability sampling. Learn about the specific types of sampling within these categories to help you with your next survey.
Probability sampling methods
With probability sampling, each element of the population has a definite, non-zero probability of being used in the sample. This method guarantees that the entire population is represented in that selection. There are several types of probability sampling methods, including:
Simple random sampling
Simple random sampling is the purest type of probability sampling. With this method, individuals are chosen randomly, giving each member of the population an equal chance of being selected as the subject.
In a systematic sample, individuals are selected at regular intervals. For example, every 10th person on the population list may be selected to participate. This method assures that the population is sampled evenly.
Before a stratified sample is taken, the population is divided into groups based on characteristics pertinent to the research, such as age or gender. The population is then randomly sampled within these specific strata. This complex method of sampling ensures each category of the population is represented in the sample.
With cluster sampling, every member of the population is assigned to a group known as a cluster. A sample of clusters is chosen using a probability method like random sampling, and only individuals within the sampled cluster are surveyed.
Multistage sampling uses several different probability sampling methods. For example, your sampling process may begin with cluster sampling. Then, you use simple random sampling to choose a subset of participants from each cluster to create the final sample.
Non-probability sampling methods
With non-probability sampling techniques, the sample is collected based on specific criteria, so not every member of the population has a chance of being selected. These sampling methods are often used for online surveys. The different types of non-probability sampling include:
In a convenience sample, individuals are selected for how easily accessible they are to the researcher. This method is typically used during preliminary research phases.
Quota sampling is similar to stratified sampling, except it assigns a quota to each population subset, meaning that the sample must include a specific number of individuals from each group.
With judgment or purposive sampling, the researcher selects individuals for a specific quality relevant to the study. For example, if you want to study what it takes to graduate summa cum laude, you would survey individuals who graduated with that distinction.
In a snowball sample, you rely on your initial survey respondents to refer you to new participants.
A voluntary sample is made up of people who volunteer to take part in the survey. Typically, these respondents have a strong interest in the survey topic.