Why Sample Size Questions Are Among the Most Common in Any Viva
Regardless of discipline or methodology, Malaysian postgraduate viva examiners ask about sample size in almost every examination. “Why did you choose twenty participants for your qualitative study?” “Is 150 respondents sufficient for structural equation modelling?” “How did you determine that your sample was large enough?” These questions are not designed to undermine your study — they are standard evaluations of whether the student understands the relationship between sample size and the claims their study can make. Knowing how to answer sample size questions in your Malaysian viva confidently and specifically is therefore one of the most universally applicable viva preparation tasks.
The critical thing to understand before preparing your answers is that there is no single universal criterion for sample adequacy. The right sample size depends on your research design, your research questions, your analytical approach, and your epistemological framework. Your answer to sample size questions should demonstrate that you understand what principle of adequacy applies to your specific study and that your sample meets that criterion.
Justifying Qualitative Sample Sizes
For qualitative research — particularly interview-based or focus group-based studies — sample size adequacy is most commonly evaluated against the criterion of saturation. Theoretical saturation or data saturation is reached when additional participants are no longer producing new codes, themes, or insights — when the data collected from the next participant is essentially confirming patterns already identified in previous participants’ data rather than adding genuinely new dimensions.
When answering sample size questions in a Malaysian viva for a qualitative study, explain the saturation criterion and describe how you monitored for saturation during your data collection. “I continued interviewing participants until I noticed that new interviews were producing no additional themes or dimensions not already represented in the data — this occurred at approximately the fourteenth interview, and I conducted two further interviews to confirm saturation before closing data collection, giving a final sample of sixteen.” This answer demonstrates methodological understanding specific to qualitative research and provides a principled justification rather than an arbitrary number.
If your study used a purposive sample designed for depth and specificity rather than saturation — for example, a focused case study involving a small number of key informants — justify this on epistemological grounds: “The study aimed to understand the decision-making processes of senior administrators in a specific institutional context. A purposive sample of six participants — all of whom held direct decision-making authority in the relevant processes — was appropriate because the goal was depth of understanding about a specific phenomenon, not generalisability across a population.”
Justifying Quantitative Sample Sizes
For quantitative research, sample size adequacy is evaluated against statistical power — the probability that your study would detect a statistically significant effect if one truly exists. Sample size determination in quantitative research is ideally conducted a priori, before data collection, using power analysis based on the expected effect size, the desired statistical power level (typically 0.80), and the significance threshold (typically .05). If you conducted a priori power analysis before your study, be prepared to explain it: what effect size you assumed, what power level you targeted, and what sample size this calculation recommended.
If your sample size was determined by practical constraints — available participants, time, budget — rather than by formal power analysis, acknowledge this honestly while explaining what it means for the statistical power of your study. “The sample of 180 participants was determined by the number of students enrolled in the programme during the study period rather than by formal power calculation. Post-hoc power analysis using G*Power indicated that this sample provides adequate power (0.82) to detect medium effect sizes at α = .05, though smaller effects may have been missed.” This honest acknowledgement, paired with a post-hoc verification, demonstrates statistical literacy even when the ideal a priori process was not followed.
Handling the Generalisation Question
A follow-up to sample size questions frequently asked in Malaysian vivas is the generalisation question: “Can you generalise from this sample to a broader population?” This question requires understanding the specific type of generalisation your study can and cannot support. Quantitative studies with probability samples can support statistical generalisation to the population from which the sample was drawn — but only to that population, and only within the confidence intervals your analysis produces. Quantitative studies with convenience samples cannot support statistical generalisation and should acknowledge this as a limitation.
Qualitative studies cannot support statistical generalisation from their samples to populations by design — this is not a weakness of qualitative research but a feature of its epistemological framework. Qualitative findings support analytical or theoretical generalisation: the insight, pattern, or theoretical development produced by the study may be transferable to other similar contexts, but this transferability is evaluated by readers who assess the richness of your description and the similarity of the new context, not by statistical criteria. Being able to articulate this distinction clearly — qualitative studies produce transferable insights, not statistically generalisable results — demonstrates the kind of methodological self-awareness that examiners in Malaysian postgraduate examinations are specifically looking for when they ask about your sample.
Preparing Your Sample Size Answer Before the Viva
Prepare a two-to-three-minute spoken answer to the sample size question for your specific study before the viva. Write it out, then practise saying it aloud until you can deliver it fluently without notes. Your answer should include: the type of sample you used, the criterion of adequacy you applied, how you determined that your sample met this criterion, what the implications of your sample size are for the claims you make in your conclusions, and how you acknowledge and address any limitations arising from sample size in your thesis.
Knowing how to answer sample size questions in your Malaysian viva confidently is not just about having a prepared answer — it is about demonstrating that your sampling decisions were deliberate, principled, and appropriate for the research questions you were addressing. That demonstration of methodological consciousness is what distinguishes a candidate who conducted research thoughtfully from one who simply followed a procedure.
