Sampling is a significant factor of a scientific approach that determines the validity and reliability of any research. By definition, a sample is a representative group of a population observed to generalize the findings (Ary, Jacobs, Sorencen, & Walker, 2014). The sampling strategy depends on the research design and research method. Sampling requires an understanding of key terms and identification of a target population.
There are two major sampling procedures available: probability and non-probability. In probability sampling, everyone has an equal chance to be selected, whereas, in the non-probability selection, subjects are chosen by a researcher. Probability sampling includes simple, systematic, and stratified random sampling. A non-probability sample includes quota, convenience, purposive, and snowball sampling. All of them have distinct advantages and disadvantages (Ary et al., 2014).
A research design is a detailed description of how research should be conducted regarding data collection and data analysis. A successful research design must identify the purpose of the study and research questions, a method used to gather, process, and analyze the data.
Data collection is also a significant step in conducting research. It is used to gather information about the studied phenomenon. Data can be collected with such tools as the survey, quantitative or qualitative interview, questionnaire, focus groups, or observation (Ary et al., 2014). Depending on the research design, a researcher can choose one or multiple appropriate tools. Likewise, each device is used according to its advantages and disadvantages. For instance, an online survey best fits quantitative research with a probability sampling, whereas a focus group is better for qualitative research with a non-probability sample.
During the research, every step requires careful study and identification. A research design provides a framework for data collection and analysis. Access to data defines the sampling, and therefore the data collection method.
Ary, D., Jacobs, L.C., Sorencen, C., & Walker, D.A. (2014). Introduction to research in education 9th edition. Wadsworth, NV: Cengage Learning.