Sampling method

Sampling method

1. Stratified Sampling

   • Explanation
     • Essential characteristics of the population that it has to reflect (age, occupation, language and so on). Study these characteristics in the target population (for example, age distribution). Recruit participants randomly, but in a way that keeps the same proportions in the sample.
   • Advantages
     • Control representativeness of some key characteristics without relying on chance. Useful when the researcher is certain characteristics are essential and when the sample sizes are not large.
   • Disadvantages
     • Requires more knowledge about characteristics of the population; harder to implement
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2. Random Sampling

   • Explanation
     • List of all members randomly select a sub-set. This way all the members have equal chance of becoming part of the sample.
   • Advantages
     • If the sample size is sufficient, researchers may be certain that even unexpected characteristics are fairly represented in the sample.
   • Disadvantages
     • It is practically impossible to carry out truly random sampling, for example, the target population might be geographically dispersed.
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3. Self-selected sampling

   • Explanation
     • Recruiting volunteers: newspaper advertisements. Anyone who wants to participate is included in the sample.
   • Advantages
     • A quick and easy method to recruit participants while at the same time (for example, many different people read newspapers).
   • Disadvantages
     • Representativeness and generalization are limited.
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4. Opportunity sampling

   • Explanation
     • Recruiting participants that are easily available, for example, undergraduate psychology students.
   • Advantages
     • Useful when financial resources are limited. In some studies, there may be reasons to believe that people are not that different. For example, some basic properties of memory or sense perception may be common for most people and are independent of culture, education or other characteristics.
   • Disadvantages
     • Generalization from opportunity samples is very limited. For example, psychology students are typically familiar with experimental procedures.
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5. Purposive sampling

   • Explanation
     • A sample that is selected based on characteristics of a population and the objective of the study.
   • Advantages
     • The flexibility of purposive sampling allows researchers to save time and money while they are collecting data.
   • Disadvantages
     • When people know that they’ve been selected for a research project, then it can change their behaviour. They might choose to act in a way that the researchers to reach the conclusions that they expect to see, or the opposite issue can occur as well.
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6. Snowball sampling

   • Explanation
     • Snowball sampling can be used to reach hard-to-reach populations. Participants or informants with whom contact has already been made can use their social networks to refer the researcher to other people who could potentially participate in or contribute to the study.
   • Advantages
     • It allows for studies to take place where otherwise it might be impossible to conduct because of a lack of participants. Snowball sampling may help you discover characteristics about a population that you weren’t aware existed.
   • Disadvantages
     • It us usually impossible to determine the sampling error or make inferences about populations based on the obtained sample.
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