Most of the times, researchers get confused while conducting a qualitative study through FGDs. Most of the Books of Research Methods have different answers for the above questions. What is a suitable number of participants in a FGD?
How many FGDs are sufficient for a M.Phil. or Ph.D. study? Lets see, what is the opinion of our scholars?
Assuming FGD is focus group discussion, then, as a starting answer, I think that a researcher will be looking for a judged sufficient number of participants to enable varied opinions on the topic under discussion. There's no set rule; it's a judgment call, based on, among other things, available resources for doing the research.
The number of participants will vary according to the nature of your research topic and the participants' relationship to that topic. If they will be talking about an issue where they are highly engaged, then this would point to a smaller group -- possibly 4-6, while low engagement would point to a larger group size -- possibly 7-9.
As for the number of groups, this will depend on saturation, i.e., the point at which a new group no longer generates any new content. This is likely to occur around 5 or 6 groups, but there is not guarantee. In particular, if there are a wide range of opinions and experiences with your topic, it take more groups to reach saturation.