How many qualitative interviews is enough?

How do you choose the number of participants?

So this week I have mostly been battling with my methodology and research design sections, desperately trying to get a handle on how to justify all the choices I will have to make. You see, probably like many researchers out there, I know what I want to do and how I want to do it – I even know why I want to do it. But….my opinion is not justification for the viva, so I need to wade my way through a huge amount of reading to demonstrate that I have made my decisions wisely, and not just on a whim.

A minefield of qualitative research methods terminology

The reading itself isn’t a problem – a lot of it is really interesting and will definitely help me when I come to actually carrying out my data gathering stages. The issue is trying to remember the differences between all the approaches/methods/designs and understanding that they all overlap each other, not to mention that people use interchangeable terminology for some of them – a sure fire way to confuse someone brand new to sociology!

So I have had to take a bit of a step back this week and take it one question at a time. My current question is – how many interviews/case studies do I want to carry out? How many researchers do I want to work with to gather their experiences? I have been reading a review paper from the National Centre for Research Methods which aims to tackle exactly that: How many qualitative interviews is enough?


It all depends on context and your research aims

Something which the paper immediately explains is that, really, there is no clear answer to this, that it depends completely on the aims of your research and the context they sit in. This is something I can definitely relate to. For me, the emphasis is very much on the depth of the data – I want to gather a very rich, deep set of data based on lived experiences – something which I know will be time-consuming in nature. This will natuarlly have an effect on the number of researchers I carry out these activities with.

Predicting the future and the saturation principle

The paper also covers the fact that you wont always be able to predict the number of interviews needed, as this could change during the course of your research. The main reason for this would be if you are adhering to the saturation principle; in that you continue to carry out interviews until you stop receiving any new or different information. In my case, I don’t think this would be an option as I am gathering lived experience data and, as far as I can guess, there would always be new experiences and difference emerging, so no cut off point would be reached.

Quality over quantity

There does not seem to be a straightforward answer to my questions – I think for now, the answer is to focus on the fact that I am gathering ‘how’ and ‘why’ data, rather than ‘what’ data, so the depth of the data itself is more significant than the numbers. One way I might choose to frame the number of studies is to consider subject areas/schools/departments, as I am keen to frame these lived experiences in the context of the academic field to ensure the outcomes are relevant to academics and practitioners in their own fields.