Hello, I want to know, how I can decide about a sample size? I have a massive online open course with 70,000 students (health professionals) and I want to explore, by a qualitative methodology, the barriers and facilitators of taking this course, even in regions with bad connectivity.
We need to know more about what you want to achieve or find out. Assuming you want more than ‘This is what a few people said….’ the sample size needed would be the same as for any study – the largest possible. Scale is a key element in the trustworthiness of a study. The method of data collection – interview, ftf, postal, Skype etc. – is irrelevant. 100 cases begins to look reasonable, unless internal comparison are made when you would need 100 per comparator. And so on.