Qualitative Research: Methods, Process and Example

„How many interviews do I need?“ is the question almost every empirical thesis starts with, and most guides answer it with „it depends“. Solid numbers on this have existed for twenty years.

Qualitative research is an approach that studies a small number of cases in depth in order to understand how people experience, interpret and explain something. It asks open questions instead of fixed response options, selects its cases by criteria rather than at random, and analyzes language rather than numbers. By the end of this article you will know which method fits your question, how to justify your sample size, and when a different design would serve you better.

📌 The key points

• Qualitative research goes deep, not wide.
• Saturation appeared after twelve of sixty interviews (Guest 2006).
• Cases are selected by criteria, never by random sampling.
• In-depth interviews and focus groups are the most common methods.
• Most student interview studies require IRB review before data collection.

What is qualitative research?

Qualitative research is the umbrella term for every empirical method whose result is an interpretation rather than a measurement: it gathers text, images and sound, places that material in its context, and reconstructs the meaning the people studied attach to their own actions.

The research guide of the USC Libraries opens with a warning worth taking seriously: „there is considerable variation in how a qualitative research study is organized“ (USC Libraries, Qualitative Methods). Unlike an experiment, there is no single template you can fill in, which is exactly why your methods section has to explain your own choices rather than recite a standard procedure.

The contrast with quantitative research begins with the question itself. If you want to know what percentage of students watch the news in the evening, you need numbers. If you want to know why someone stopped and what that changed about their day, you need an account. Both questions are scientific, but they call for different tools.

Qualitative research does not tell you how many. It shows you how and why.

The limit of the approach follows from that same design. Because cases are chosen deliberately rather than at random, the findings apply to those cases first and not to a wider population. That is the design, not a flaw. Where the open, material-led way of thinking comes from is covered in the article on deductive and inductive research.

Qualitative or quantitative: what actually differs

The difference between qualitative and quantitative research is not the sample size but the question you are trying to answer. A study with twelve participants is not qualitative because twelve is a small number, but because it collects open answers and interprets them.

The belief that qualitative simply means „few cases“ is stubborn, and it costs points every semester. If you send out 200 questionnaires with five open text fields and then count how often each answer appears, you have worked quantitatively, however open the questions were. A study with eight carefully coded interviews, by contrast, remains qualitative.

The two terms themselves are explained in the article on qualitative vs quantitative. If you want the advantages and drawbacks of both approaches side by side, you will find them collected under qualitative and quantitative research methods.

Qualitative data collection methods

Qualitative data collection methods differ mainly in how close they get to the situation you want to learn about. An interview captures one person's interpretation. An observation sees the behavior itself. A content analysis works with material that came into being without your involvement.

The choice therefore follows the research question rather than personal preference. If you are after motives and reasoning, there is almost no way around a conversation. If you are after routines the participants themselves barely notice, observation is more honest than any follow-up question. And if your subject already consists of texts or images, you do not need to interview anyone at all.

The in-depth interview: the standard choice for student projects

The in-depth interview, usually run as a semi-structured conversation, is by far the most common method in student work, because it produces rich material for a manageable amount of effort. You prepare an interview guide of open questions, then follow it loosely rather than slavishly, probing wherever something interesting appears. The guide is a handrail, not a script. How to word those questions is covered in detail under qualitative surveys.

Qualitative observation: open rather than pre-coded

Qualitative observation is frequently confused with its quantitative counterpart. The moment you set up a fixed tally sheet in advance and simply count instances in the field, you are collecting frequencies and therefore working quantitatively. Observation stays qualitative as long as you write detailed field notes instead of counting. Whether your categories come from theory or emerge from the material is a separate, independent decision.

⚠️ Caution

Running an observation with a ready-made tally sheet and calling it „qualitative“ in your methods section misdescribes your own procedure. Decide before you enter the field whether the categories are fixed in advance or emerge afterwards, and write exactly that into the paper.

How many interviews do you need?

How many interviews you need cannot be derived from a formula, but there are empirical reference points: in the study by Guest, Bunce and Johnson (2006), saturation occurred within the first twelve of sixty interviews, and the basic elements of the overarching themes were present after as few as six.

Saturation here means the point at which further conversations stop producing new themes. Guest and his colleagues counted this systematically in their own material rather than simply asserting it, and their paper is still cited heavily on this question (Guest, Bunce and Johnson 2006: How Many Interviews Are Enough?, Field Methods 18(1), pp. 59 to 82).

Saturation: the documented ranges

A systematic review by Hennink and Kaiser (2022) analyzed 23 papers on saturation, 17 of which used empirical data of their own. Across those 17 the range turned out to be remarkably narrow: saturation was reached at 9 to 17 interviews or 4 to 8 focus group discussions. The authors state a condition explicitly, and it matters more than the figure itself: this applies above all to relatively homogenous study populations and narrowly defined objectives (Social Science & Medicine 292, article 114523).

Two terms are easily confused here, and the difference belongs in every methods section. The figures above measure when no new themes appear. Theoretical saturation in grounded theory means something else: the point at which no theoretically relevant differences are left to find. Justifying a sample size with the wrong concept is a common and avoidable slip.

How to justify your sample size

Two things follow for your own work. First, ten to fifteen interviews are a defensible range for a narrowly framed undergraduate or master's project. Second, as soon as your group is mixed, you are comparing states, backgrounds or age groups, or you are looking for fine differences in meaning, you will need more, and the figures above no longer carry your justification.

💡 Tip

Never put the sample size into your methods section as a bare number. Write it as a decision with a reason: „Eight interviews were planned because all participants had been through the same program. After the seventh conversation, no new themes emerged.“ Those two sentences make the number traceable; a bare figure stays open to challenge.

If you are writing for publication, the APA reporting standards for qualitative research, known as JARS-Qual, set out what a manuscript has to disclose about the sample and the analysis (APA Style, JARS-Qual). They were introduced in 2018 and are worth reading before you write the methods section, not after.

Sampling in qualitative research

Sampling in qualitative research follows criteria rather than chance. Where a quantitative study draws at random so that the sample mirrors the population, you deliberately look for the cases in which your subject shows itself most clearly.

Calculating a sample size the quantitative way is therefore the wrong math here. What you are after is range, not the average. Someone researching reasons for dropping out will deliberately seek both the first-year engineering student and the education major weeks away from graduation. Only the contrast between the two shows what the cases have in common.

Two routes are common

• Purposive selection: you set the criteria from your theory before entering the field.
• Theoretical sampling: you decide after each case who you need next.

With theoretical sampling the sample is not fixed in advance but develops as the study proceeds, and you stop once no theoretically relevant differences are left to find. For a thesis with a fixed submission date the first route is usually the realistic one, because with the second you cannot say when you will be finished.

How a qualitative study is judged at the end is a separate question: objectivity, reliability and validity come from the quantitative tradition and do not transfer unchanged. Which frameworks apply instead is covered under quality criteria in qualitative and quantitative research.

IRB review before your first interview

IRB review has to happen before you record your first interview, not once the transcripts are sitting on your laptop. Research with human participants at US institutions falls under the federal regulations at 45 CFR 46, and starting data collection without approval can make the data unusable.

The framework goes back to the Belmont Report and its three principles of respect for persons, beneficence and justice. Subpart A of 45 CFR 46, „also known as the Common Rule, provides a robust set of protections“, and fifteen federal departments and agencies adopted it in 1991 (HHS Office for Human Research Protections, 45 CFR 46).

Where the line usually runs for students

• Senior thesis or independent research: IRB approval is required.
• A class exercise that stays inside the course: usually outside IRB oversight.
• Results presented publicly or reused by your instructor: review is required.
• Anything involving minors, patients or incarcerated people: expect a longer process.

Duke University states the rule for the first case plainly, listing „Senior thesis, independent research“ as work for which IRB approval is required (Duke University, IRB review of student research). Your own institution's policy is what actually governs your project, so check it before you contact a single participant.

One point of terminology, because it trips people up in transatlantic reading: in the United States a thesis is normally the master's-level work and a dissertation the doctoral one. In the United Kingdom the two words are commonly used the other way round.

The process of a qualitative study

The process of a qualitative study runs from question to finding in six steps, and unlike a survey you are allowed to go back. If you notice at step four that the interview guide is missing the point, you revise it and conduct the next conversations differently.

That flexibility is not a license to improvise silently. Every change to the procedure has to be documented, otherwise nobody can follow the study afterwards. What you describe in the methods section must match what actually happened.

1. Sharpen the question. „How do students experience the news?“ becomes „How do juniors in education explain having stopped watching the news in the evening?“. Only that narrowing makes case selection decidable. More on this under criteria for good research questions and hypotheses.
2. Choose the method and justify it. Interview, observation or content analysis follows from the question. Write the reasoning down in a paragraph; it belongs word for word in the methods section later.
3. Select cases and secure access. Who do you need, how many, and through which route do you reach them? Access to the field causes most delays in practice.
4. Collect and record. Test the recorder, obtain written consent, arrange a quiet room. An unusable recording costs you the whole conversation.
5. Transcribe and code. Sound becomes text, text becomes categories. Budget generously, as typing up takes several times the length of the conversation.
6. Analyze and situate. Categories become statements, and statements are set against the literature.

For the analysis itself, thematic analysis and qualitative content analysis are the two routes most commonly taught. Whichever you choose, name it in the methods section and follow its steps. How data collection fits into the wider research process is covered in the article on data collection.

When qualitative research is the wrong choice

Qualitative research is the wrong choice as soon as your question asks for a quantity, a proportion or a tested relationship. Twelve interviews tell you which explanations exist, not how widespread they are, and that confusion produces a findings section any committee member can pull apart.

In these six cases you need a different design:

• Your question begins with „how many“, „how often“ or „how strongly“.
• You want to make a claim about a whole group rather than your cases.
• You want to compare two time points or two groups statistically.
• Your advisor has explicitly asked for a significance test.
• You have no access to people willing to talk to you at length.
• You have fewer than eight weeks left for fieldwork and analysis.

The time budget is the point most often underestimated. Between the first scheduling email and finished coding, twelve interviews take several weeks of pure working time, and most of that is transcription. IRB review adds to that clock, not to the time before it.

The mistake about cause and effect

You will often read that qualitative research uncovers cause and effect. That holds only in a very narrow sense. An interview tells you which connection a person themselves draws between two things, which is a valuable finding in its own right. Whether that connection holds beyond the individual case has not been tested. A tested claim about effects requires a hypothesis-testing design and a sufficiently large, randomly drawn sample.

Mixed methods: both routes together

Qualitative and quantitative components can be combined, a design known as mixed methods. Three basic forms are common: both strands in parallel, qualitative first and quantitative second, or quantitative first with a qualitative strand to explain the findings. The deciding question is which of your questions cannot be answered by one approach alone. One honest warning belongs here: in practice the two strands are rarely brought together properly, and two rounds of data collection almost always mean substantially more work.

Qualitative research example

A qualitative research example makes the steps easier to picture than any definition. Suppose you are writing your thesis on news avoidance and want to know why young people stop following the news.

The example is invented, the procedure is not: this is how an interview study in a thesis actually runs, from the first narrowing of the question to the sentence that ends up in the limitations.

The research question

„How do students aged 20 to 26 explain having deliberately cut down their news consumption?“ The question is narrow enough for a thesis and open enough to invite accounts. You do not need a hypothesis here, because you are exploring rather than testing.

Choosing the method

You settle on the in-depth interview, because you need reasoning and interpretation, and both only appear in conversation. Observation is out, since news avoidance consists of not doing something. A diary study would be possible but demands weeks of commitment and would answer the question only indirectly.

The sample size

You plan twelve interviews. The justification: the group is homogenous in age and life situation, the question is narrowly framed, and for exactly this constellation the review by Hennink and Kaiser (2022) reports a range of 9 to 17 interviews. After the eleventh conversation no new patterns appear, and the twelfth confirms the finding.

The analysis

You transcribe every conversation, read each twice, and assign categories close to the wording: overload, the same bad news over and over, powerlessness, a deliberate time limit. You then summarize how the categories relate to each other and set the result against existing research.

What you can claim, and what you cannot

Your finding reads: there are four recurring patterns of explanation for news avoidance, and three of them describe exhaustion rather than indifference. What you cannot say is what percentage of college students in the US avoid the news. That sentence belongs in your limitations, and it makes the thesis stronger rather than weaker.

Conclusion

Qualitative research is worth choosing whenever you want to understand how people experience and explain something. Decide early and write the reasoning down, because advisors reward a decision they can follow more highly than a method that merely looks demanding. A small, well-justified interview study beats a large survey without a concept.

Where to go next

• Want to build your interview guide? How to create a questionnaire
• Need the overview of every phase? The empirical research process
• Want to know how qualitative surveys are analyzed? Qualitative surveys: forms and analysis
• Looking for the foundations? Empirical research: definition and guide

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