When interviewing: how many is enough?

Year 2020, Volume: 7 Issue: 1, 73 - 79, 01.04.2020

William Cobern Betty Adams

https://doi.org/10.21449/ijate.693217

Cited By: 18

Abstract

Researchers need to know what is an appropriate sample size for interview work, but how does one decide upon an acceptable number of people to interview? This question is not relevant to case study work where one would typically interview every member of a case, or in situations where it is both desirable and feasible to interview all target population members. However, in much of qualitative and mixed-methods research and evaluation, the researcher can only reasonably interview a subset of the target population. How big or small should that subset be? This paper provides a brief explanation of why the concept of generalization is inappropriate with respect to the findings from qualitative interviewing, what wording to use in place of generalization, and how one should decide on sample size for interviews.

Keywords

Research methodology, Sample size, Generalization, Interview research, Qualitative research, External validity

References

• Baker, S. E., & Edwards, R. (2012). How many qualitative interviews is enough? Expert voices and early career reflections on sampling and cases in qualitative research. National Centre for Research Methods Review Paper. Retrieved December 28, 2019 from http://eprints.ncrm.ac.uk/2273/4/how_many_interviews.pdf
• Channell, A. C. (2019). Teacher and Parent Perspectives on Alignment to The Next Generation Science Standards Following Teacher Professional Development. (PhD), Western Michigan University, Kalamazoo, MI.
• Cobern, W. W., Gibson, A. T., & Underwood, S. A. (1999). Conceptualizations of Nature: An Interpretive Study of 16 Ninth Graders' Everyday Thinking. Journal of Research in Science Teaching, 36(5), 541 564. DOI.org/10.1002/(SICI)1098 2736(199905)36:5<541:AID-TEA3>3.0.CO;2-1
• Cronbach, L. J. (1975). Beyond the Two Disciplines of Scientific Psychology. American Psychologist, 30(2), 116-127. DOI:10.1037/h0076829
• Ellis, P. D. (2010). Effect Size FAQs. Retrieved December 20, 2019 from https://effectsizefaq.com/about/
• Gobo, G. (2007). Sampling, representativeness and generalizability. In C. Seale, G. Gobo, J. F. Gubrium, & D. Silverman (Eds.), Qualitative Research Practice. SAGE Publications: Thousand Oaks, CA, p. 405-426. ISBN-13: 978-0761947769.
• Kukull, W. A., & Ganguli, M. (2012). Generalizability: the Trees, the Forest, and the Low-Hanging Fruit. Neurology, 78(23), 1886-1891. DOI:10.1212/WNL.0b013e318258f812.
• Royall, R. M. (1986). The Effect of Sample Size on the Meaning of Significance Tests. The American Statistician, 40(4), 313-315. DOI:10.2307/2684616
• Seidman, I. E. (2006). Interviewing as Qualitative Research: A Guide for Researchers in Education and The Social Sciences, 3rd Edition. Teachers College Press: Columbia University, New York. ISBN-13: 978-0807746660.
• Teo, T. (2013) (Ed.). Handbook of Quantitative Methods for Educational Research. Sense Publishers: Rotterdam, The Netherlands. ISBN: 978-94-6209-404-8.