Sampling methods in qualitative and quantitative research

Why does sample size not matter in qualitative research? Because of the assumptions that qualitative researchers make, namely, that the social world is not predictable. Qualitative researchers believe that people are not like molecules or other objects; people’s actions are not predictable.

But quantitative researchers DO believe that social activity IS predictable. So when they compare their observations of social activity to what would happen in purely random results, the difference says something. Let’s say you were to research people’s preferences for a particular interactive feature. Say you’re wondering if young people will like a radio button more than older people. First, you model what results you’d expect if you’d just flipped a coin. Then you use a probability (random) sample, and compare those results to purely random results. Is there a difference?

If there is a difference between them, you can infer that indeed, something other than chance (in this case, age) affect people’s preferences.

Qualitative researchers don’t agree that such things can be reliably predicted. That’s why they don’t bother with expensive and involved random sampling. See all these details below from my research design course.

Qualitative versus quantitative research, Part II

Thousands of people arrive at this blog wanting to know what is the difference between qualitative and quantitative research. Qualitative versus quantitative research is by far the most popular post on this blog. In that first post, I explained why sample size doesn’t matter in qualitative research. In this post, I explain why qualitative research is generally a better approach for design research.

Notice how the qualitative process is iterative with the going back and forth from data to sense-making or developing theory. It is flexible and can change direction easily.

Qualitative design process

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And the quantitative design process is very linear, and does not include an iterative component:

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If your design process involves an iterative prototyping phase, for example, then qualitative research is likely the best approach for you. Notice also that qualitative research necessarily involves the researcher putting herself in the shoes of the user. Quantitative research does NOT require the researcher to see through the eyes of the user.

Designers often want to empathize with their users. They want to understand their experiences and pain points. They want to know what their users are thinking. This is why qualitative research is often better suited to design research.

See also this embedded slideshow from my research design class. This should give you the basic differences between the two.