Issues of Theoretical Sampling: A Narrative Review

Context: Theoretical sampling is the hallmark of grounded theory methodology, but there seems to be little information accessible to researchers regarding process and guidance concerning theoretical sampling. The current study aimed to have a comprehensive and thorough review of the related studies on theoretical sampling and examine definitions, challenges, differences and applicable tips about this type of sampling to provide a comprehensive and clear picture of the sampling process and its probable challenges as well as explaining its practical aspects. Objectives: The ultimate goal of all the explorations is to provide practical sources for researchers to answer their questions about theoretical sampling. Data Sources: Databases such as ProQuest, Scopus, Pubmed, Science Direct, Wiley, Ovid, Google Scholar, and also Magiran, SID and Iran Medex (Persian databases) were searched from 1967 to 2015 using keywords of theoretical sampling and qualitative sampling. Study Selection: A total of 562 Persian and English studies were found. According to the inclusion and exclusion criteria thirty articles and nine books were examined thoroughly. Data Extraction: The narrative literature review was used as the most appropriate method to manage the data. Results: Definitions and characteristics of theoretical sampling; theoretical sampling of data archive; the difference between theoretical, purposeful and selective sampling; saturation and credibility in theoretical sampling were discussed in results. Conclusions: The current study indicated disagreements about some theoretical definitions and operational applications of theoretical sampling; however, the general consensus was that researchers explicated the decision making process in detail. Researchers should justify the selection and the sequence of sampling process to explain the complicated process of analytical abstraction and theory development by empirical data. Hence, the credibility of their theory and research is enhanced.