This introductory text provides an overview of the article “Sample Size for Interview in Qualitative Research in Social Sciences: A Guide to Novice Researchers” by Wasihun Bezabih Bekele and Fikire Yohanes Ago. Published in Research in Educational Policy and Management, Volume 4, Issue 1 (2022), pages 42-50, the article addresses a persistently controversial question among qualitative researchers: “how many interviews are enough for one qualitative research project?”.
Purpose and Problem Addressed: The authors aim to provide guidance to novice researchers who frequently encounter the challenge of determining an appropriate sample size for qualitative research, especially when planning proposals or seeking funding. The core problem is that it is often difficult to define the number of participants before actual data collection. While the concept of “theoretical saturation” is often used to justify sample size, the authors note that saturation can only be recognized during data collection, which doesn’t solve the problem for initial budgeting or proposal requirements.
Key Findings and Factors Influencing Sample Size: The article highlights that there is no universally guiding rule for deciding the required number of samples in qualitative research; rather, “it depends”. The authors endeavor to identify the various circumstances or factors upon which this decision depends. These factors are recommended to be considered by researchers when deciding on a justifiable sample size prior to data collection or at the proposal stage.
The decision on “How many” interviews depends on several factors, including:
- The focus of the research.
- The type of research question.
- Available resources and time.
- Institutional committee requirements.
- The judgments of the epistemic community in which a researcher is located.
- The nature of the selected group or sample composition, specifically its homogeneity or heterogeneity. Heterogeneous samples typically require a larger size.
- The domain of inquiry, especially if it is diffuse or vague.
- The experience of the researcher with qualitative research.
- The scope of the study: A broader scope requires more participants, more interviews, and more data sources.
- The nature of the topic: Complex, new, or sensitive topics that are not easily noticeable or where participants are uncooperative may require more participants.
- The quality of data: If data are on target, rich, and experiential, or if participants are articulate and willing to share, fewer participants may be required to reach saturation.
- The qualitative method and study design used.
Numerical Suggestions and Controversy: The sources reveal that while specific numerical guidelines are sought, there is no concrete, clear, and easy guideline for less experienced researchers. The most frequently observed range of sample size in qualitative research is 20-60. However, the article details various suggestions depending on the research design and context:
- For narrative research, which often focuses on individual life stories, 1 or 2 persons are typically sufficient.
- Phenomenological studies are suggested to have at least 6 participants (Morse, 1994), or between 5 and 25 interviews (Creswell, 1998).
- Ethnographies and grounded theory studies are commonly suggested to involve approximately 30-50 participants (Morse, 1994), or 20-30 for grounded theory (Creswell, 1998), and 30-60 for most ethnographic studies (Bernard, 2000).
- Some scholars suggest 6-8 interviews for a homogeneous sample and 12 to 20 when trying to achieve maximum variation (Kuzel, 1992). A general suggestion of 6-12 interviews is noted as potentially sufficient for one qualitative research project, but with important caveats regarding sample heterogeneity, data quality, and domain complexity.
- For publication, Warren (2002) suggests a minimum of 20-30 interviews, while Gerson and Horowitz (2002) contend that fewer than 60 interviews cannot support convincing conclusions, and more than 150 produce too much material to analyze effectively.
The authors conclude that these differing numerical suggestions highlight the difficulty in specifying minimum sample sizes. Ultimately, while there’s no universal agreement, researchers are advised to be clear and confident about their sampling method, why they used it, and why their chosen sample size is appropriate. The article emphasizes that research with larger and more heterogeneous samples is more likely to be published in notable journals.
Reference: Bekele, W. B., & Ago, F. Y. (2022). Sample Size for Interview in Qualitative Research in Social Sciences: A Guide to Novice Researchers. Research in Educational Policy and Management, 4(1), 42-50. https://doi.org/10.46303/repam.2022.3