Behnam - you seem to be 'quantifying' your qualitative study. Pilot's are not usually needed for qualitative research - and 'instruments are not tested'. If you simply want to member-check a semi-structured interview schedule - then you could run it by a 'potential' participants or by a few trusted colleagues who have experience in qualitative interviewing.

Behnam - Qualitative research requires small sample size. The pilot study is good in qualitative research but the number of participants will be very small. For a full study in a qualitative research approach, the number of interviews to be conducted depends on several factors: 1) Qualitative research typically require a smaller sample size than quantitative research, 2) The sample size in any qualitative study mainly depends on the concept of saturation and the goal of qualitative researchers should be the attainment of saturation. Saturation occurs when adding more participants to the study does not result in additional perspectives or information, 3) The number of data collection methods (e.g. observations, open-ended survey, focus group interviews etc) does play a role in sample size. The method of triangulation helps to reach the researcher to a saturation much earlier if you rely on interviews and the number could be as small as 10-15 interviews only. You can use theoretical sampling which involves selecting participants based on specific characteristics. Following some initial interviews, the researcher will analyze the data. Based on the results from this round of data analysis, the researcher will identify more people to interview. These might be people who will confirm what the researcher has already found, but the researcher will also purposefully look for participants who can dis-confirm the previous findings. The researcher will conduct interviews with those newly selected participants and then analyze them. Theoretical sampling continues like this, moving back and forth between sampling, data collection, and analysis, until the researcher reaches data saturation, or the point at which the researcher fails to collect new information with subsequent interviews.

Behnam - you seem to be 'quantifying' your qualitative study. Pilot's are not usually needed for qualitative research - and 'instruments are not tested'. If you simply want to member-check a semi-structured interview schedule - then you could run it by a 'potential' participants or by a few trusted colleagues who have experience in qualitative interviewing.

I would like to add that, since qualitative research is flexible, one possibility is to "pilot" your study "on the progress". I mean, you can carry out your first interview and use your experience and feed-back to eventually make some changes on the subsequent ones...

Thank you Antonio M. Oller-Marcén Dean Whitehead Dr Manzoor Hussain for your valuable answers.

Following..

Hi there, pilot studies are certainly useful for qualitative research. They can be used to identify social/cultural norms that might be challenging for the main research, as well as to identify some meaningful direction for further interviews. This is a good way of 'ground truthing' your assumptions coming from the literature. As for sample size, this depends very much on the population size, and the demographics you wish to capture in the main research. The important thing is to ensure that the breadth of people you wish to interview are likely to correctly interpret your initial questions and avenues for discussion. I did something similar for my doctoral research. I was working in rural Victoria and my pilot work enabled me to establish a 'shared language/narrative' that was meaningful to the rural agencies I was working with, as well as farming communities. PM me if you wish to discuss further :)

The following papers may further help:

• Kim, Y. (2011) The pilot study in qualitative inquiry: Identifying issues and learning lessons for culturally competent research, Qualitative Social Work, 10, 2, pp. 190-206.
• O'Cathain, A., Hoddinott, P., Lewin, S., Thomas, K. J., Young, B., Adamson, J., Jansen, Y. J., Mills, N., Moore, G. and Donovan, J. L. (2015) Maximising the impact of qualitative research in feasibility studies for randomised controlled trials: guidance for researchers, Pilot and feasibility studies, 1, 1, pp. 32-43.
• Wray, J., Archibong, U. and Walton, S. (2017) Why undertake a pilot in a qualitative PhD study? Lessons learned to promote success, Nurse Researcher, 24, 3, pp. 31-35.

Minimum of 30.

PROCEDURE this simple procedure may help:

1. Construct your sample questions as a test set.

2. Select 10 people to answer your test set. Do 3 to 5 sets of 10 people.

3. Score your issue of interest as 1 and else 0

4. Find P and Q by P = (s + 1) / (n + 2) and Q = 1 - P

5. Use the following formula to find you sample size.

n = (Z2PQ) / e2

where Z = critical value of your confidence interval. See Z table; PQ defined above; and e = error level (if confidence interval is 0.95, then e = 0.05). This sample size may be used as guide for your pilot testing (when as how did you come up with that size of pilot test).

You do not need to know population size. There is no N in the Cochran formula. Assume non-finite population because you are taking test samples of 10 elements for 3 to 5 sets. Why 10? Easy to see pattern and give data for P and Q. Now you should have n1, n2, n3 from the test sets you calculated. You should have consistent sizes from the three sets, i.e. n1 = n2 = n3. If the differences are large, expand to 5 sets, etc.

LINK:

http://ijecm.co.uk/wp-content/uploads/2014/11/21131.pdf