Hello!
I am doing a qualitative / quantitative PhD and just wondering what people's opinions are about how many interviews is enough in terms of rigour / validity (dreaded viva!) etc?
I have 2 studies completed - 18 interviews in the first populations, and 45 in the second - this was longitudinal and involved 15 participants followed over 2 years (all interviews were between 35 minutes and an hour)....I hope to use the data from these to develop a questionnaire, itself quite a significant study...I think I have enough data...just curious about what people think?

I assume your goal is saturation with the interviews - no no themes emerging? Guest, et al, (2006) found that saturation occurred in ethnographic research within the first twelve interviews, with meta-themes present as early as six interviews. They suggest using samples of 12 participants per group of interest when examining how two or more groups differ along a given dimension. (Guest, Greg, Arwan Bunch, & Laura Johnson 2006 How Many Interviews are Enough? An Experiment with Data Saturation and Variability. Field Methods, 18 (1): 59-82.)
Hope this helps

Hi Whenever, doc08,

also think that saturation is the key. Would think that you have enough information, I plan to do a lot less interviews (however focus groups).

Doc08, thanks for your entry referring to the literature, that is actual helpful information for me as well

It also depends on the research method you are using - with discourse analysis, saturation is not the key, as one is not aiming for any kind of comprehensiveness or generalisability. Although im guessing that with combining it with questionnaires, then you are not going the constructionist route....

i agree with Doc2008 and Rick. saturation is the key. i admire you though cause that's a lot of work interms of transribing and analysis. Whats your topic on if you don't mind me asking?