I have used case-studies of the total number 20 teachers to write their journals on teaching English . During the defence,I was asked by the two assessors why 20 ? Is there any scale in qualitative research methods for a sample size? I couldn't justify my choice of the population.
Everything you need to know is in Vogt, W. P., Gardner, D. C., & Haeffele, L. M. (2012). When to use what research design. New York: Guilford Press. It's my favourite for all time. Required reading for all my supervisees. Get a copy now, also of W. Paul Vogt's other books.
On p. 149, you'll find that "20 to 40 interviewees is a normal range" but also, that the sampling size depends on (1) population you're interested in and (2) the type of research question. That's why bigger is not always better (as it is in surveys).
Various versions of this question have been asked many times here on RG. I suggest you use the search function to find and read those previous discussions.
I do not believe that there is a specific formula.
Qualitative research does not use "sampling." It is not generalizable. Rather it is intended to explore the experiences and perceptions of the participants richly, in detail.
You want data from enough people to represent your context fairly. Another way to say that is that you want "data saturation" or information from enough people so that you are not missing something that is important.
Twenty sounds like a reasonable number to me, as long as you make their demographics clear.
The question from your committee member may have come from someone who is not familiar with qualitative methodology, or the person may have been testing you.
Everything you need to know is in Vogt, W. P., Gardner, D. C., & Haeffele, L. M. (2012). When to use what research design. New York: Guilford Press. It's my favourite for all time. Required reading for all my supervisees. Get a copy now, also of W. Paul Vogt's other books.
On p. 149, you'll find that "20 to 40 interviewees is a normal range" but also, that the sampling size depends on (1) population you're interested in and (2) the type of research question. That's why bigger is not always better (as it is in surveys).
Hi,
In qualitative analysis one uses mostly case studies since there is no need for sampling the population. So, actually you used 20 case studies to make a point. The results of this analysis cannot be inferred to a larger population, so it seems that the assessors' question was posed out of curiosity , trying to figure out why you used 20 examples.
I got your point ... I think you are right as one of them asked me why I mentioned the total number of EFL teachers in Oman.
It depends on your research questions .. The higher the number of sample the more reliable and valid the data are..
In support of David’s comments, similar/useful questions/discussions (with recommended publications) can be found on RG, examples being that:
- What is ideal sample size in qualitative research ?: https://www.researchgate.net/post/Whats_is_ideal_sample_size_in_qualitative_research
- What is the basis of sampling in qualitative case study?: https://www.researchgate.net/post/What_is_the_basis_of_sampling_in_qualitative_case_study
- Hi, would you please share the sample size of the qualitative research and how did you calculate it?: https://www.researchgate.net/post/Hi_would_you_please_share_the_sample_size_of_the_qualitative_research_and_how_did_you_calculate_it
- What are your thoughts on ‘saturation’ in qualitative research?: https://www.researchgate.net/post/What_are_your_thoughts_on_saturation_in_qualitative_research
For qualitative sample size you best look into how the responses fit your saturation degree. I did a study using interviews and its demanding work but it looks simple. Check this as a sample of reference and even read how analysis was done: Chapter Waqf Development in Light of Islamic Economics in the Muslim...
Hope it will help.
The sample size should be mentioned as 30 participants as Creswell (2003) has mentioned in RESEARCH METHODS. Another option will be ok if you do the sampling until the saturation point.
- Badges
- Science topic
- Similar topics
- Mathematics
- Statistics
- Sampling Design
- Sample Size