Krueger and Casey suggest that when you’re selecting participants for focus groups, it’s important to keep in mind how selecting participants might impact data quality. We need to ask ourselves what types of people will provide the most insight into the discussion, rather than trying to focus on including all the different perspectives.
It is best to aim for homogeneity within the group, but make sure there is enough variation among participants to allow for different opinions. In order to achieve homogeneity, a few screening questions may be necessary, but be careful as this may hint to the participant what the research is about.
Focus group participants are often selected from a small sample of people, and therefore we need to be careful not to over generalise our findings. Best practice favours having a focus group consisting of strangers rather than acquaintances because participants that know each other may influence each other’s answers. Conversation might not always flow as freely between strangers, so it’s important the moderator encourages each participant to contribute.
1 Krueger, R. A., & Casey, M. A. (2009). Participants in a Focus Group. In Focus Groups: A Practical Guide for Applied Research (4th ed). Los Angeles: SAGE.