Sampling in Qualitative Research
Qualitative researchers select their participants based on their characteristics and knowledge as they relate to the research questions being investigated. As you already know, the researchers’ primary concern is to explore individuals in their natural context, and they have little interest in generalizing the results beyond the participants in the study.
The sampling procedure most often used in qualitative research is purposeful sampling. According to Patton (1990), “The logic and power of purposeful sampling lies in selecting information-rich cases for study in depth. Information-rich cases are those from which one can learn a great deal about issues of central importance to the purpose of the research”
Sampling in Quantitative Research
Unlike their qualitative counterparts, quantitative researchers are interested in generalizing from their group of participants, the sample, to the larger population from which the sample was drawn. Various decisions regarding the participants must be made by the researcher in order to maximize the generalizability of the study
In some situations, even these realistic populations may not be so realistic. For example, surveying all the fifth-grade teachers in New York City or high school principals in Pennsylvania might exceed the study’s resources. In addition, the researcher must be able to obtain a complete list of persons in the realistic population.
Some researchers refer to this as the sampling frame. For teachers, administrators, and school districts, researchers can consult their state education department and state educational organizations to obtain these lists.
Types of Random Sampling
The most important aspect of sampling is that the sample must represent the larger population from which it is drawn. Random sampling is a technique or tool that produces essentially a inversion of the initial population. Random sampling is conducted in such a way that every person in the population has an equal and independent chance of being selected.
This means that when a person is selected, it does not affect the chances of anyone else being selected. Take, for example, a technique often used in grade school spelling lessons. Remember your elementary teacher asking everyone in your class to form a line and to count off by ones and twos to establish teams of spellers?
No, the moment you got in line with your classmates and the teacher said, “Okay, count off by ones and twos,” your group membership was decided. If your best friend, immediately to your left, was a one, then you had to be a two—and there was no chance that the two of you would be on the same spelling team. This scenario violates the requirement that the selection of one person cannot have an effect on whether another person is chosen or not.
Simple Random Sampling
Simple random sampling involves the random selection of individuals from the realistic population as a whole. First, the researcher must obtain a complete list of names for all individuals who make up the realistic population. To select a simple random sample, each person on the list of the realistic population is assigned a number.
For example, if the list contains the names of 20 individuals, then the number 01 is assigned to the first person on the list, and number 02 to the second person on the list, and so on, until all 20 people on the list have been assigned a number.
A sample is a group or individuals that a researcher uses in a study. Samples are composed of what are referred to as “participants.” Depending on the type or approach of the study, a sample would be selected from a larger population in different ways. Qualitative researchers focus on selecting participants based on a certain characteristic that they wish to investigate and are not interested in generalizing their findings beyond the settings they are studying.
Purposeful sampling is a common procedure used in qualitative research that identifies key informants or persons who have specific knowledge about the topic being studied. The type of purposeful sampling that a researcher may decide to use depends on the purpose of the study.