Qualitative vs Quantitative Research: How to Choose an Approach

"Should my research be qualitative or quantitative?" is one of the first methodology questions students ask. It is also one of the most misunderstood, because many students choose an approach first and then try to fit a question around it.

This guide explains the difference between the two approaches, when combining them makes sense, and how to choose and justify an approach for your own thesis, dissertation or research project.

The short version

Quantitative research works with numbers. It measures, counts and tests relationships between variables, usually with larger samples and statistical analysis. It tends to answer questions such as how many, how much, how often or is there a relationship between X and Y.

Qualitative research works with words, meanings and experiences. It explores how people understand, experience or explain something, usually with smaller samples and interpretive analysis. It tends to answer questions such as how, why and what is it like.

Neither approach is better. They are tools for different jobs, and the right one is the one that fits your research question.

Key differences at a glance

	Quantitative	Qualitative
Main aim	Measure, test, compare	Explore, understand, interpret
Typical data	Numbers, scales, counts	Interview transcripts, observations, documents
Common methods	Surveys with closed questions, experiments, secondary datasets	Interviews, focus groups, observation, document analysis
Sample	Often larger, aiming for generalisation	Often smaller, chosen for depth and relevance
Analysis	Descriptive and inferential statistics	Thematic analysis, coding, content or discourse analysis
Quality criteria	Validity, reliability, generalisability	Credibility, transparency, reflexivity, transferability
Typical question words	How many, to what extent, is there a relationship	How, why, in what ways, what is it like

These are tendencies, not strict rules. A survey can include open questions, and qualitative data can sometimes be counted. What matters is the overall logic of your study.

Start with your research question

Your research question is the strongest guide to your approach. Look at what it asks you to find out.

If it asks you to measure something, compare groups or test a relationship, it points towards a quantitative approach.
If it asks you to explore experiences, understand meanings or explain a process in depth, it points towards a qualitative approach.
If it has two parts, for example measuring a pattern and then explaining it, it may point towards mixed methods.

If you are still shaping your question, the research question builder can help you test whether it is focused enough, and our article on how to find a research gap explains where good questions usually come from.

Practical factors that also matter

Once your question points in a direction, check whether that approach is realistic for your project.

Access to participants or data. A quantitative survey usually needs enough respondents to support the analysis you plan. Qualitative interviews need people willing to talk in depth. Can you reach them within your timeframe?
Time. Transcribing and coding interviews takes longer than many students expect. Cleaning and analysing survey data also takes time, especially if you are new to statistics software.
Skills. Are you comfortable with statistics, or with interpretive analysis? Both can be learned, but plan time for it.
Ethics. Most studies involving people need ethical approval or at least a review. Check your university's process early, as it can affect your timeline.
Expectations in your field. Some disciplines and departments lean towards one approach. Look at recent theses in your department and at the studies in your literature review.
Language. If you are interviewing in one language and writing in English, think about translation and how you will present quotations.

When mixed methods make sense

Mixed methods research combines quantitative and qualitative data in one study. It can be powerful, but it is not automatically better, and it roughly doubles the work.

Mixed methods can make sense when:

your question genuinely has a "how much" part and a "why" part;
you want to use interviews to design a better survey;
you want to use interviews to explain unexpected survey results.

Mixed methods are less suitable when they are added only to look more thorough, or when your time and word count cannot support doing both parts well. A focused single-method study is usually stronger than a stretched mixed-methods one. If you are considering it, discuss it with your supervisor first.

How to justify your choice

Examiners do not only look at which approach you chose. They look at whether you explained why. A clear justification usually covers four points:

Fit with the question. Show how the approach matches what your question asks.
Fit with the literature. Explain how your choice relates to the methods used in previous studies.
Practical feasibility. Briefly show that the approach is achievable with your access, time and resources.
Limitations. Acknowledge what your approach cannot show, and explain why that is acceptable for your aims.

This paragraph is an illustrative structure only. Your justification must reflect your own study and the methodology sources recommended by your department.

Common mistakes and a quick checklist

Common mistakes

Choosing by comfort. "I don't like statistics" is understandable, but it is not a justification. Let the question lead, then adapt the question if needed.
Mismatched question and method. Asking "to what extent" and then interviewing five people, or asking "how do people experience" and then using only closed survey questions.
Treating qualitative as easier. Good qualitative research needs careful sampling, systematic analysis and transparency about your role as researcher.
Overclaiming. Generalising from a small qualitative sample, or claiming that a correlation proves cause.
Ignoring your department's guidance. Some programmes have specific expectations about methods, ethics or methodology chapter structure.

Quick checklist

My research question clearly indicates what kind of knowledge I need.
My approach matches the question words I use.
I have checked access, time, skills and ethics requirements.
I can explain how my approach relates to methods in the literature.
I have noted the limitations of my approach.
I have discussed my choice with my supervisor.

Frequently asked questions

Is qualitative research less scientific than quantitative research?

No. The two approaches have different aims and different quality criteria. Qualitative research is judged on things like credibility, transparency and the care taken in analysis, while quantitative research is judged on validity, reliability and appropriate statistics. Both can be done well or badly.

How many interviews or survey responses do I need?

There is no single number that applies to every study. It depends on your question, your method, your field and your university's expectations. Check your module guidance, look at comparable studies, and agree a realistic target with your supervisor.

Can I change my approach after I start?

Sometimes, especially early in a project, but it can affect your ethics approval, timeline and methodology chapter. If you think your approach no longer fits, talk to your supervisor before collecting more data, and document the reasons for any change.

If you would like to work through these decisions on your own project, our thesis chapter planner can help you map your methodology chapter, and the research proposals guide explains how to present your approach in a proposal.

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