Which factors are considered when determining the sample size for a qualitative study?

When it comes to qualitative research, a number of factors need to be considered when organizing sample sizes. Below are four points to keep in mind when thinking about sample size:

Quality over quantity

Qualitative market research aims to tease out insights from a specific demographic, whether they are Midwest moms with household incomes above $60k, teens who play specific video games, or B2B decision makers. The main objective when conducting qualitative market research is ensuring the right people are recruited for the study. Depending on the study, pulling from a broad geographic region may be necessary for more accurate insights. As market researchers will tell you, there are wildly divergent opinions and experiences depending on where a person lives.

Researchers look for study respondents who meet all the criteria identified from quantitative research studies, in addition to the criteria set forth by the clients through their own research. Melding the populations from client lists and quantitative research will generate high-quality panels, rather than just recruiting from a general population. The quality of the output from well-curated panels is well worth the effort it takes to recruit them.

Choose the appropriate study design

The type of the qualitative study will determine the best sample size for your research. Will the study require in-depth interviews, ethnographic research, or focus groups? Some studies will blend all three, and perhaps more. Depending on which method or methods being used will determine the appropriate sample size. Each methodology for gathering feedback yields different outcomes. Experienced market researchers will quickly know which study design is best suited to the type of outcome their client is looking for. Equally important to the study design is the quality of questions being asked of the participants. An experienced and well-trained market researcher knows how to probe to get more nuanced answers from participants in a study group. Getting to the “how” and “why” is what makes qualitative market research so useful.

Pay attention to the Principle of Saturation

Sample sizes need to be large enough to adequately address the research questions being asked; however, too large a sample size brings the risk of repetitive data, also known as saturation. Market researchers know they have the appropriate sample size in a study when they’ve reached the saturation point. In other words, when answers or themes start becoming repetitive, the researcher can then shut down the study, knowing that saturation has been reached. There is diminishing return with larger samples, and more is not always better.

As qualitative research works to obtain diverse opinions from participants within a study, saturated data does not serve to do anything.

The objective of a qualitative study is to have a large enough sample size to expose a diversity of opinions while limiting the sample size at the point of saturation.

Does a magic number exist for qualitative research sample sizes?

After considering the above factors, there actually is a “magic” number for sample sizes. Based on research 30 seems to be an appropriate number for the most comprehensive assessment. Some studies are successful with as few as 10 participants, but this depends heavily on the quality of screening and recruiting the most appropriate participants.

If possible, in-depth interview studies should aim for sample sizes between 20-30, paying special attention to demographic and geographic profiles of your study recruits.

To learn more about recruiting the most appropriate participants for your next market research study, contact us here.