Work out focus group size instantly with clear inputs, formula shown and shareable results.
Focus group size is a trade-off between diversity of view and individual airtime. Eight participants in a ninety minute session share 11.25 minutes each on average, which is workable; twelve participants leaves 7.5 minutes and the quieter members effectively silent. Four groups of eight gives 32 participants and six hours of recorded discussion.
Airtime per participant
minutes = session length / participants per group
Total participants
total = participants per group x number of groups
Six to eight for most topics. Sensitive subjects work better with four to six, and market research sometimes uses ten to twelve accepting shallower input.
Usually three to five per distinct population segment, continuing until no new themes emerge - the same saturation logic as interviews.