Sampling and Sampling Techniques

Sampling is the process of selecting members of a research sample from a defined population, usually with the intent that the sample accurately represents the population. A sample comprises the individuals, items, or events selected from a larger group referred to as a population. Sampling error is the deviation of a sample statistic from its population value.

Types of Sampling Techniques

1. Convenience sampling. It is a group of cases that are selected simply because they are available and easy to access
2. Probability sampling. This is a procedure for drawing a sample from a population such that each individual in the population has a known chance of being selected
3. Purposeful sampling. It is the process of selecting cases that are likely to be “information-rich” with respect to the purposes of a qualitative research study
4. Cluster sampling. Employed in selecting naturally occurring groups in the population.
5. Criterion Sampling. Employed in selecting a group of cases that satisfy particular specifications or standards
6. Proportional stratified random sampling. It is a technique in which the proportion of each subgroup in the sample is the same as their proportion in the population
7. Purposeful random sampling. Employed in selecting by random sampling methods for the purpose of establishing that the selection of cases was not biased.
8. Random sample or simple random sampling. Employed in selecting participants such that all members of the accessible or target population have an equal and independent chance of being selected
9. Snowball sample. Employed in selecting participants by asking one person to recommend someone suitable  as a case of the phenomenon of interest, who then recommends another person who is a suitable case or who knows potential cases; the process continues until the desired sample size is achieved.
10. Systematic sampling. This is a type of sampling in which individuals are selected from a list by taking every nth name.
11. Purposive sampling. In here, the researcher selects a sample based on his or her experience or knowledge of the group to be sampled.
12. Quota sampling. It is most often used in survey research when it is not possible to list all members of the population of interest.
13. Random assignment. This is the process of assigning individuals or groups to the experiment and control treatments such that each individual and group has an equal chance of being in each treatment.