Qualitative research explores meaning and experience using non-numerical data such as interviews and observations, and answers ‘how’ and ‘why’ questions. Quantitative research measures and tests using numerical data such as surveys and statistics, and answers ‘how many’ and ‘what relationship’ questions. Which you choose depends on your research question.
Choosing between qualitative and quantitative research is one of the first big decisions in a dissertation or research project, and getting it right shapes everything that follows. The two approaches collect different kinds of data, answer different kinds of questions, and are analysed in completely different ways, so the choice is not a matter of preference but of fit with what you are actually trying to find out. This guide explains what each approach is, sets out the key differences side by side, and shows how to decide which suits your own research question, so your methodology rests on a clear, justified choice rather than a guess.
What is qualitative research?
Qualitative research explores meaning, experience and context using non-numerical data, usually words. It asks open questions about how and why something happens, and gathers rich, detailed data through methods such as interviews, focus groups, observations and the analysis of documents or texts. Because it aims for depth rather than breadth, it typically uses smaller, purposively chosen samples, and the data is analysed by identifying themes and patterns rather than by counting. Qualitative research is well suited to understanding people’s perspectives, motivations and experiences, and to exploring topics where the important questions are not yet well defined. Its findings are detailed and contextual, though usually less generalisable to a wider population than numerical results.
What is quantitative research?
Quantitative research measures and tests using numerical data. It asks questions about how much, how many, or what the relationship is between things, and gathers data through methods such as surveys with closed questions, experiments and structured measurements. Because it aims for breadth and generalisability, it typically uses larger samples chosen to represent a wider population, and the data is analysed statistically. Quantitative research is well suited to measuring the scale of something, comparing groups, and testing hypotheses about relationships between variables. Its findings can often be generalised beyond the sample, though they tend to offer less depth and context than qualitative data, telling you what is happening more clearly than why.
Qualitative vs quantitative: the key differences
The two approaches differ across every stage of a project, from the question to the analysis. The table sets the main contrasts side by side.
| Aspect | Qualitative | Quantitative |
| Data | Non-numerical: words, meaning | Numerical: numbers, measurements |
| Question | How and why | How many, how much, what relationship |
| Methods | Interviews, focus groups, observation | Surveys, experiments, measurements |
| Sample | Smaller, purposively chosen | Larger, representative |
| Analysis | Themes and patterns | Statistics |
| Aim | Depth and understanding | Breadth and generalisability |
| Findings | Rich and contextual | Generalisable, less detailed |
Neither approach is better in the abstract; they are simply suited to different questions. A project that wants to understand how patients experience a treatment calls for qualitative depth, while one that wants to measure whether the treatment reduces symptoms across a population calls for quantitative measurement. The skill is matching the approach to the question, which is exactly what a marker looks for when assessing your methodology.
When should you use each approach?
The deciding factor is always your research question. Use qualitative research when you want to explore, understand or interpret, when the topic is not yet well understood, or when meaning and experience are central. Use quantitative research when you want to measure, compare or test, when you need results that generalise to a wider group, or when the key questions concern amounts, frequencies or relationships between variables. A useful test is to look at the verb in your research question: words like explore, understand and describe point towards qualitative work, while words like measure, compare and test point towards quantitative work. If your question contains both kinds of aim, that is often a sign you should consider combining the two.
What is mixed-methods research?
Mixed-methods research combines qualitative and quantitative approaches in a single study, using each for what it does best. A researcher might, for example, run a survey to measure how widespread an attitude is, then conduct interviews to understand why people hold it, so the numbers show the scale and the words explain the reasons. Mixed methods can give a fuller picture than either approach alone, but it also asks more of you, since you have to design, carry out and analyse two kinds of data and then integrate the findings. For that reason it is powerful when the research question genuinely needs both, but it is not a way to avoid choosing; a mixed-methods study still has to justify why each approach is there.
How do you choose for your dissertation?
For a dissertation, the choice of approach belongs in your methodology, where you justify it against your research question rather than simply stating it. Start from what you are trying to find out, decide whether that calls for depth, breadth or both, and then choose the approach and methods that fit, explaining why they suit the question and why the alternatives do not. Practical factors matter too: the time you have, your access to participants or data, and the skills the analysis will require. Our how to write a dissertation methodology guide covers how to write this section and justify your choices, and framing that choice well begins at the proposal stage, which our research proposal example guide walks through.
Common mistakes to avoid
- Choosing an approach out of preference rather than fit with the research question.
- Using a large survey to answer a question that really needs the depth of interviews, or the reverse.
- Treating mixed methods as a default, without justifying why both approaches are needed.
- Describing your chosen approach without justifying why it suits your specific question.
- Applying the wrong analysis, such as looking for statistics in qualitative interview data.
A clear, justified choice of approach is the foundation of a strong research project, and it makes every later stage easier. For fitting your methodology into the wider structure of your work, see our how to structure an assignment guide.
Frequently asked questions
What is the difference between qualitative and quantitative research?
Qualitative research explores meaning and experience using non-numerical data such as interviews, while quantitative research measures and tests using numerical data such as surveys and statistics. They answer different kinds of question.
Which is better, qualitative or quantitative research?
Neither is better in general; each suits different questions. Use qualitative research to explore and understand, and quantitative research to measure, compare and test. The right choice depends on your research question.
Can you combine qualitative and quantitative research?
Yes. Mixed-methods research combines both, using numbers to measure scale and words to explain reasons. It gives a fuller picture but requires designing and analysing two kinds of data, so it should be justified by the question.
How do I choose between qualitative and quantitative research?
Start from your research question. Words like explore and understand point to qualitative research; words like measure, compare and test point to quantitative. Choose the approach that fits what you are trying to find out.
