After deciding which approach to use in a research study, it is now time to decide where or from whom to collect the needed data. To do this, some important terminologies must be first defined. What is a population? How about a sample?
A population is the complete group of persons, animals, or objects that possess the same characteristics that are of the researcher’s interest. There are two kinds of population—target and accessible. The target population is made up of all research elements that the researcher would want his/her findings to be generalized to, while the accessible population is a group of research elements within which the research respondents will be taken from. For instance, in a study that seeks to find out the opinion of Filipino high school students regarding the K to 2 basic education program, the target population are high school students in the Philippines, while the accessible population may be those from the locality of the researcher.
Most of the time, data are collected from some members of a population called samples. A sample is a group of individuals that represents the characteristics of a population. In a population of Filipino high school students, the members are all high school students in the country. High school students from two schools in each region would be members of the sample. The process of choosing samples from a population is called sampling.
In quantitative research, the purpose of sampling is to generalize its findings in the population; while in qualitative research, the sampling focuses on an in-depth understanding of a phenomenon or situation.
The following are the advantages of sampling in qualitative research:
- It saves time, effort, and resources. Dealing with a smaller number of participants is easier than taking the whole population.
- It minimizes casualties. In some studies, the respondents are needed to be examined thoroughly, thus, resulting to withdrawal of some respondents from the roster. The withdrawal of considerable number of respondents is crucial, especially when only few of them are selected. Therefore, sampling of the correct number of respondents needed for the study prevents undesirable casualties.
- It paves the way for thorough investigation. Since the research respondents are only small in number, the researcher could focus on each respondent and do a thorough examination on them. More time of observation could be spent if there is a manageable number of respondents.
- It allows easy data handling, collection, and analysis. A small number of research respondents allows the researcher to manage his/her data collection and analysis procedures rather than doing it with a large number.
How do we determine the number of samples needed in the study? When determining the sample size for qualitative research, it is important to remember that there are no hard and fast rules. There are, however, at least two considerations on sample size in a qualitative investigation:
- What sample size will reach saturation or redundancy? That is, how large does the sample need to be allowed for the identification of consistent patterns? Some researchers say the size of the sample should be large enough to leave the researcher with “nothing left to learn.” In other words, one might conduct interviews, and after the tenth one, realize that there are no new concepts emerging. That is, the concepts, themes, etc. begin to be redundant.
- How large a sample is needed to represent the variation within target population? That is, how large must a sample be in order to assess an appropriate amount of diversity or variation represented in the population of interest?
The sample size is estimated based on the approach used in the study or the data collection method employed. However, experts prescribe numbers for sample sizes in some qualitative research studies. Cited from Creswell (2013), one to ten subjects are recommended for phenomenology (Dukes, 1984), 20 to 30 individuals for grounded theory (Charmaz, 2006), four to five respondents for case study, and single culture-sharing groups for ethnography.
