How many qualitative interviews is enough?

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National Centre for Research Methods Review Paper  
How many qualitative interviews  is enough? 
Expert voices and early career reflections on sampling and cases in qualitative research 
Sarah Elsie Baker, Middlesex University 
Rosalind Edwards, NCRM, University of Southampton


Abstract
Students conducting a piece of qualitative research frequently ask ‘how many interviews is enough?’ Early career researchers and established academics also consider this question when designing research projects. In this NCRM Methods Review paper we gather and review responses to the question of ‘how many’ from 14 renowned social scientists and 5 early career researchers. The riposte to the question of ‘how many’ from most contributors is ‘it depends’. In considering what ‘it depends upon’ however, the responses offer guidance on the epistemological, methodological and practical issues to take into account when conducting research projects. This includes advice about assessing research aims and objectives, validity within epistemic communities and available time and resources
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Gotta Number Fetish?

Whether it's ethics committees, research supervisors, grant funders or journals you'll always find someone with a number fetish...forget saturation, they'll be more impressed with your study if it simply has more participants?

Have you had this experience? Feel the pressure to put 40 people into your narrative inquiry study? (by the way that would take about three years to analyse)

Numbers are not the key to quality qualitative research simply because generalisability is not the aim...qual research sacrifices generalisability for depth of meaning, you learn important things from local phenomenon rather than going for representativeness...

The key to determining how many participants to have is based on saturation in many instances...

Volume 11, No. 3, Art. 8 – September 2010 Forum:Social Qualitative Research

Sample Size and Saturation in PhD Studies Using Qualitative Interviews

Mark Mason

Abstract: A number of issues can affect sample size in qualitative research; however, the guiding principle should be the concept of saturation. This has been explored in detail by a number of authors but is still hotly debated, and some say little understood. A sample of PhD studies using qualitative approaches, and qualitative interviews as the method of data collection was taken from theses.com and contents analysed for their sample sizes. Five hundred and sixty studies were identified that fitted the inclusion criteria. Results showed that the mean sample size was 31; however, the distribution was non-random, with a statistically significant proportion of studies, presenting sample sizes that were multiples of ten. These results are discussed in relation to saturation. They suggest a pre-meditated approach that is not wholly congruent with the principles of qualitative research.

Key words: saturation; sample size; interviews

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..........but saturation isnt always the key....you may do a study that aims to sample a rare group of people, for example...this sampling is called Deviant Case or Extreme Sampling...you may also be working with a finite group of people as in Participatory Action Research...you may have only one case, as in autoethnography...