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By Julia Schaefer

Unlike quantitative research, numbers matter less when doing qualitative research.

It’s about quality, not quantity. So what’s in a number?

When thinking about sample size, it’s really important to ensure that you understand your target and have recruited the right people for the study. Whether your company is targeting moms from the Midwest with household incomes of $70k+, or teens who use Facebook for more than 8 hours a week, it’s crucial to understand the goals and objectives of the study and how the right target can help answer your essential research questions.

Determining the Right Sample Size For Qualitative Research Tip #1: Right Size for Qualitative Research

A high-quality panel includes much more than just members who are pulled from a general population. The right respondents for the study will have met all the criteria line-items identified from quantitative research studies and check the boxes that the client has identified through their own research. Only participants who match the audience specifications and background relevance expressed by the client should be actively recruited.

Determining the Right Sample Size For Qualitative Research Tip #2: No Two Studies are Alike

Choosing an appropriate study design is an important factor to consider when determining which sample size to use. There are various methods that can be used to gather insightful data, but not all methods may be applicable to your study and your project goal. In-depth interviews, focus groups, and ethnographic research are the most common methods used in qualitative market research. Each method can provide unique information and certain methods are more relevant than others. The types of questions being studied play an equally important role in deciding on a sample size.

Determining the Right Sample Size For Qualitative Research Tip #3:  Principle of Saturation and Diminishing Returns

Understanding the difference of which qualitative study to use is very important. Your study should have a large enough sample size to uncover a variety of opinions, and the sample size should be limited at the point of saturation.

Saturation occurs when adding more participants to the study does not result in obtaining additional perspectives or information. One can say there is a point of diminishing returns with larger samples, as it leads to more data but doesn’t necessarily lead to more information. A sample size should be large enough to sufficiently describe the phenomenon of interest, and address the research question at hand. However, a large sample size risks having repetitive and redundant data.

The objective of qualitative research is to reduce discovery failure, while quantitative research aims to reduce estimation error. As qualitative research works to obtain diverse opinions from a sample size on a client’s product/service/project, saturated data does benefit the project findings. As part of the analysis framework, one respondent’s opinion is enough to generate a code.

The Magic Number? Between 15-30

Based on research conducted on this issue, if you are building similar segments within the population, InterQ’s recommendation for in-depth interviews is to have a sample size of 15-30. In some cases, a minimum of 10 is sufficient, assuming there has been integrity in the recruiting process. With the goal to maintain a rigorous recruiting process, studies have noted having a sample size as little as 10 can be extremely fruitful, and still yield strong results.

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