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Determining the Best Sample Size

Creating Your Study

7 min read

The #1 question we get asked by researchers is this: How many people should I include in my study? We’ll answer that in two ways:

    • What the academics say
    • What our experience has taught us

The academic POV

What constitutes an adequate sample size has been debated extensively in the market research industry for many years, in part because quantitative sample sizes are statistically easier to measure, including variance.

Often, quantitative research mindsets get applied to qualitative research because quant norms are concrete, whereas qualitative sample sizes are difficult to prove mathematically.

Studies have been published over the years on the topic of adequate sample sizes for qualitative research. Here are a few:

    • Creswell, Glaser, Morse (the recommendation: 30–50 participants)
    • Springer (Springer puts forth the argument that anywhere from 5–50 is adequate, but that 25–30 is considered to be the right number)
    • InterQ (recommends 20–30)

Broadly, the academic research suggests that a sample size in the 30–50 participants range achieves what experts call “the point of saturation” where adding another participant doesn’t add materially to the insights generated. We agree with that analysis.

What our experience has taught us

Qualitative research is more art than science. 

Typically, clients turn to qualitative methods to understand deeper meaning: beliefs, attitudes, perceptions, feelings, emotion and more—deep intangibles that help add up to the “why.” So while we believe that minimum sample sizes should be employed in qualitative research, getting to the “why” requires more nuance. For this we recommend taking 10 critical variables into consideration.

The 10 critical variables

We have found that there are 10 critical variables to consider for determining the right sample size for a qualitative research study.

1. Where you are in the process
Earlier stage projects (e.g. exploratory or generative studies) can generally employ smaller sample sizes, because more iteration and development will be conducted as the project progresses.

2. Business impact
The higher the business impact of the research, the greater the sample size should be. For high impact research, we would likely recommend a hybrid quant/qual approach so you’re not relying solely on qualitative research.

3. Geography
One essential variable we consider is the geographic diversity of the target audience. It can be as easy as needing domestic and international respondents, or it may be more complex. In the US, most national brands have very broad distribution, so making sure to include the coasts as well as the interior is not only great practice, it’ll signal to clients that you don’t favor one type of demographic audience over another.

4. Research design
How the study is designed can have a huge impact on results. Which questions to ask in what order changes how respondents answer, affecting a study’s insights and conclusions. 

5. Research platform
When you leverage a qualitative market research platform, you are buying a tech stack. One important variable is how well equipped that resource is technologically to identify the right recruits, field the study in a relevant way, and interpret the results. In the case of Fabric, our proprietary AI is an industry first, employing sentiment and emotion analysis to help researchers rapidly make sense of video responses.

6. Quality of recruits
It’s very important that the people in the study be the right people, regardless of how many respondents are included in the study size. Beyond the issue of whether they technically qualify, the people included in the study need to “feel” like the right consumer. 

Using Fabric’s video-centric platform is particularly useful in this regard. Seeing the target in motion, on screen, telegraphs a great deal of information, versus seeing numbers in a graph or having a faceless/voiceless respondent using text replies.

7. Analysis
Who is interpreting the data your study will generate? All insight is qualitative, so considering how equipped you or your research partner is in the process has a tremendous influence on both sample size and study design.

8. Methodology
A variety of methodologies are available to the researcher, and each will suggest its own approach to sample size. Qualitative techniques to choose from include IDIs (in-depth interviews), focus groups, in-homes, friendship pairs, small group interviews, intercepts, observational research, ethnographies and/or digital (online, mobile). 

In Fabric’s case, the methodology is unique in that it’s effectively “1-on-none”—meaning it’s asynchronous, and there is no moderator present. Much has been written about the effects of group-think within focus groups, where an ‘alpha’ respondent will influence others; Fabric has none of that. Fabric also removes the moderator from the study; therefore there is no moderator bias. 

Instead, the methodology and technology employed by Fabric free up respondents to behave in a more open manner. Fabric’s confessional style enables what researchers have called the “online disinhibition effect” where respondents are more open to express themselves because there is no fear of disagreement or conflict with a moderator or fellow panelists.

9. Company culture
Some organizations are more comfortable with small sample sizes, whereas some look for larger samples because distribution is wide and/or global. For example, we have worked with Nike’s Innovation Kitchen on early exploratory studies using a small sample size. When we work with Xbox, having 10 markets each with 10 respondents, the sample size can drift to 100+ easily.

10. Segments
Often we’ll see that a client has a number of segments to understand. In that case, determining sample size depends on whether or not you’re looking for a rollup of all segments. If you’re going for a rollup, the 30–50 number is fine. 

However, if you’re seeking to understand similarities and differences amongst segments, we would recommend 15 respondents per segment. This enables your study to take advantage of our AI, which kicks in at a minimum of 15 respondents.


What is the right sample size for your qualitative study?
If you’re looking for a short answer on the recommended sample size, it’s 30–50. But keep an open mind to key variables that may influence higher or lower numbers.


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