This is a really important question in quantitative research, because those studies need to engage with a sample group to draw conclusions about the whole population. For example, before an election, pollsters will speak to a small percentage of voters and then predict how all voters will behave, and therefore, which party will win the election.

Qualitative research is different, because you’re aiming for deep understanding of a specific population, not generalised results. As such, there are fewer guidelines about the ideal number of participants.

As a rule of thumb, qualitative researchers recommend recruiting between 10 to 50 participants. The ideal number will depend on your research question, your method, your timeline, and your budget. For instance, if your research question is about very personal experiences, then it may be best to interview people, and you may only have time to engage with 6 to 8 participants. But if your research question is about group views, and you have a little more time, you could run three focus groups with 6 people per session, therefore recruiting 18 participants. It’s recommended to make a judgement call at the outset, and then again at the data analysis stage, asking: have I reached saturation point?

In other words, are you seeing recurring themes? If so, you’ve talked to enough people. If not, keep recruiting.

Remember, you need to reach saturation point for each sub-group in your study. That way, you can be confident in drawing conclusions about each of the sub-groups involved. For instance:

• If you were studying the views of all teenagers aged 13–18 years old, then you would only have one group of interest, and you’d reach saturation point when you heard similar themes coming through (e.g., two focus groups of 6 people per session = 12 participants). 
• If you were studying the views of teenagers aged 13–18 years old, but you wanted to compare boys and girls, and those who play sport versus those who don’t, then you have four sub-groups (female participants, male participants, female non-participants, male non-participants). You’d need to run two focus groups for every sub-population, so your study would be much larger (e.g., 4 x 2 focus groups with 6 people per session = 48 participants).

In a nutshell:

• Recruit at least 10–12 people in your study but aim for more if you can.
• Keep gathering data until you reach saturation point and you’re not hearing new key themes or ideas.