Ideal Sample Size in Qualitative Research
March 20, 2017
When beginning research with new clients, the questions that top their lists are often: is there an ideal sample size in qualitative research? If so, what is it?
This question is important! Size matters, albeit in a different manner than in quantitative research, where numbers are attached to statistical significance. Keep reading to explore the considerations involved in panel size and what you should be looking for in your panels when conducting qualitative research.
Quality is greater than quantity
The vast majority of our clients are hoping for market research on a select group of people. B2B decision makers in human resources. Moms who live in the Midwest and have household incomes of $70k +. Teens who use Facebook more than 8 hours a week.
Specificity is powerful! Since our client base has a good understanding of their audience type, we ensure in our qualitative panels that we’re recruiting participants who meet every criterion pinpointed by our clients and our own quantitative research. Because the type of members in a panel must fit a certain mold, panel quality is far more important than general sampling with broad parameters. Therefore, our first step is to recruit respondents who fit our audience specifications.
Study design in qualitative research
Choice of sample size is often affected by the type of qualitative study chosen to complete market research. Some of the commonly employed methods in this type of research are in-depth interviews, focus groups, and ethnographic research, and the types of questions being asked are just as important as the size of the sample used.
In all of these study designs, an important principle to keep in mind is that of saturation.
In qualitative research, in comparison to quantitative research, the goal is to reduce estimation error. When a researcher is approaching saturation, the collection of additional data does not provide further insight into the topic of investigation. Qualitative research teases out a myriad of opinions from the sample size, and even one person’s opinion generates part of a code. To borrow from economics, the principle of diminishing returns applies here with increasingly large samples; more data does not necessarily lead to more new information, but rather a repetition of the same information (hence saturation).
As such, the goal in qualitative studies is to obtain a large enough sample that a range of opinions will be represented, but not so large that the uncovered data is repetitive.
So … what is the magic number to aim for in qualitative research?
At this point, we return to our original questions:
Is there an ideal sample size in qualitative research? If so, what is it?
We’ll give you an answer this time around. Academia tells us that 30 seems to be an ideal sample size for the most comprehensive view of an issue, but studies with as few as 10 participants can yield fruitful and applicable results (recruiting excellence is even more important here!).
We generally recommend a panel size of 30 respondents for in-depth interviews if the study includes similar segments within the population. We suggest a minimum sample size of 10, but in this case, population integrity in recruiting is critical.
Want to discuss your project and the type of sample size that would work best for you? Request a proposal >