Quantitative or qualitative research: which fits your thesis or dissertation?

Your research question decides whether the study is quantitative or qualitative. Preference, comfort with statistics, and what your friends used do not decide it. A committee will ask why you chose your method, and "the question required it" is the answer that holds.

Read the verb in your question

Look at what the question asks you to do.

• "Is there a relationship between," "does X differ between," "how much," "to what extent." These ask for measurement and comparison. They call for a quantitative design, such as a survey analyzed with correlation, a t-test, or regression.
• "How do participants experience," "what meanings," "how do teachers describe." These ask for understanding and description. They call for a qualitative design, such as interviews analyzed for themes.
• Both kinds at once. Some questions need numbers for the pattern and words for the reason. These call for mixed methods.

Take the question "How does mathematics anxiety relate to course grades among first-year engineering students?" It asks about a relationship between two measured things, so a survey with a validated anxiety scale and a correlation fits. Change the question to "How do first-year engineering students describe their experience of mathematics anxiety?" and interviews fit. The topic is the same, the question is different, and so is the method.

What each approach gives you

Quantitative research produces numbers from a sample, tested statistically, and it lets you say how common something is or whether groups differ. It needs a sample large enough for your test, an instrument with evidence of reliability and validity, and analysis skills. Our guide to analyzing questionnaire data shows the steps.

Qualitative research produces rich descriptions from a small number of participants, analyzed for patterns of meaning. It lets you explain how and why, and it needs access to people willing to talk, careful interviewing, and a defensible analysis approach. See planning, conducting and reporting interviews.

Mixed methods combines both within one study. It answers more, and it costs more: two sets of data, two analyses, and a plan that shows why one alone would not do. Choose it only when your question needs it.

Check feasibility

A method that fits the question still fails if you cannot carry it out. Ask:

1. Can I reach enough participants for this method?
2. Do I have, or can I learn, the analysis skills in the time I have?
3. Does my supervisor have experience in this method?
4. Will the ethics board approve the data collection I am planning?

If an answer is no, adjust the question before you adjust the method, so the two still match.

Justify the choice in Chapter 3

Chapter 3 must say why you chose your design. State the question, the method it calls for, and a methods source that supports the link. John Creswell and J. David Creswell's Research Design: Qualitative, Quantitative, and Mixed Methods Approaches is the standard source your committee will recognize. Our guide to what Chapter 3 should include covers the rest of the chapter.

A common mistake

Students sometimes choose a qualitative design because they fear statistics, or a quantitative design because it feels more scientific. Committees see through both. Choose the method that answers the question, and defend it in writing.

Want your design tested before the committee sees it?

The Two Dissertation Moms offers a Research Design and Methodology Review that checks whether your question, design, sample and analysis fit together.