How do I defend my methodology in a viva?

Methodology questions dominate many vivas because that is where a thesis is most checkable. An examiner cannot easily verify your interpretation of a literature, and they can absolutely ask why you used this sample, this instrument, and this analysis, and whether the conclusions survive those choices.

The framing that works is decisions rather than steps. "I used semi-structured interviews" invites the question why. "I chose semi-structured over structured because the concepts were still forming and I needed participants to introduce categories I had not anticipated" answers it before it is asked, and demonstrates that the choice was made rather than inherited.

Prepare the three or four decisions an examiner is most likely to probe. Usually these are sample size or selection, the measure or instrument, the analytical approach, and anything unusual. For each, know the alternative, the reason, and what the choice cost you.

If your work is quantitative, expect the probe to land on uncertainty rather than on the test name. Kass and colleagues note that repeated measurements vary, so every quantity computed from them carries uncertainty, and they recommend reporting it through standard errors or confidence intervals while warning that standard errors can substantially underestimate uncertainty when dependencies among observations or variables are ignored (Kass et al., 2016, pp. 4-5). They also advise addressing statistical questions at the design stage, because careful data collection makes the later analysis simpler and more rigorous, and they favour starting with a simple analytical approach and adding only the complexity the data or the objective demands (Kass et al., 2016, pp. 3-4). So a good answer names the dependence structure in your data, states how you estimated uncertainty, and says what would change if that assumption failed.

If your work is qualitative, convert the word rigour into procedures an examiner can check. Korstjens and Moser set out credibility, transferability, dependability, and confirmability as the quality criteria, with reflexivity added for transparency, and they attach a strategy to each one. Thick description supports transferability, an audit trail supports dependability and confirmability, and a reflexive diary records your assumptions, values, and influence on the study (Korstjens and Moser, 2018, p. 121). That gives you four sentences to prepare: how your interpretations represent participants' views, what contextual detail would let someone judge transfer to another setting, where the record of your analytic decisions lives, and how you can show the findings came from the data.

When the question is how you know your interpretation holds, describe the process rather than asserting validity. In the study Korstjens and Moser report, two researchers analysed the first six interviews independently, compared interpretations, discussed the disagreements, and then met after every third dataset alongside regular team sessions (Korstjens and Moser, 2018, p. 122). Note that they present triangulation as a strategy to enhance credibility, not as proof of it, so claiming that triangulation validates your findings invites a follow-up you will lose. If you used interviews or focus groups, the reporting checklists are also useful preparation, since SRQR has 21 items and COREQ has 32 covering the research team, reflexivity, design, analysis, and reporting (Korstjens and Moser, 2018, p. 124).

Practical constraints are legitimate reasons and should be stated as such. "The funded period allowed twelve months of fieldwork, so I prioritized depth in two sites over breadth across six" is a real answer. Inventing a methodological rationale for a practical limit is where candidates get into difficulty, because the follow-up questions do not fit the invented story.

Bring your own list of the design's limitations. Producing it before an examiner does changes the dynamic of the conversation entirely.

Preparation for this starts well before the viva. Marino, Stefan, and Blackford recommend setting an action plan about a year before submission, reviewing progress every few weeks, and building in contingencies for technical problems, and they warn that a research project keeps generating further questions, so you have to decide what the thesis actually needs rather than chasing every possible improvement (Marino et al., 2014, p. 1). That decision is itself defensible in the viva, and it is worth noting the audience difference: Marino and colleagues write for PhD completion, while Korstjens and Moser address Master's students and junior researchers as well, so the standard of methodological detail expected of you depends on the degree.

What do I say about a choice I would now make differently?

Say exactly that, and say what you would do instead and why. Recognizing a limitation in your own design is evidence of the judgment a doctorate certifies. Defending a choice you privately know was weak is the failure mode, because examiners can usually tell.

Frame it as learning rather than as an apology. "With what I know now I would have piloted the instrument on a second site first, and the reason is that the two contexts turned out to differ in ways I did not anticipate" is a confident sentence.

Then say what it does and does not affect. A limitation that narrows the scope of a claim is different from one that undermines it, and being clear about which is what keeps the conversation constructive.

How do I handle a question I cannot answer?

Say you do not know, then say how you would find out. "I have not tested that, and the way to check it would be to compare the subgroups directly" is a strong answer. Improvising something plausible is the risk, because the follow-up question will expose it.

It is also entirely acceptable to pause, or to ask for a question to be repeated or rephrased. Examiners expect a conversation rather than a quiz, and thinking visibly is better than answering quickly and wrongly.

Nobody passes a viva by answering everything. Examiners are assessing whether you can think about your work as a researcher, and "I do not know, here is how I would approach it" is exactly that.