Why Sampling Questions Are Among the Most Probing in Any Viva
Sampling decisions are at the heart of research rigour, and examiners in Malaysian postgraduate vivas know this. The questions they ask about your sampling strategy are designed to reveal whether you understand the logic behind your choices — why you selected the participants you did, how those selection decisions align with your research questions, and what the implications of those decisions are for the claims your conclusions can make. Preparing for viva questions about your sampling strategy requires more than being able to name the sampling method you used. It requires being able to defend it as the most appropriate choice for your specific study.
The Core Sampling Questions to Prepare For
Several sampling questions appear regularly in Malaysian postgraduate vivas across disciplines. “Why did you choose purposive sampling rather than random sampling?” is common in qualitative research and requires an answer grounded in the epistemological logic of qualitative inquiry: purposive sampling selects participants based on specific characteristics relevant to the research questions, which is appropriate when the goal is depth of understanding rather than statistical representativeness. “How did you determine your sample size?” is asked in both qualitative and quantitative contexts and requires a clear, principled answer — saturation for qualitative, power analysis for quantitative, or specific criteria for sample-size recommendations in your methodology literature.
“How representative is your sample?” is a question that requires careful answering because representativeness means different things in different research paradigms. In quantitative research, representativeness refers to the statistical correspondence between the sample and the target population. In qualitative research, representativeness is not the goal — the goal is informational richness and analytical depth. Knowing which type of representativeness applies to your study and being able to articulate this distinction under viva conditions is essential preparation.
Articulating Your Inclusion and Exclusion Criteria
One of the most specific sampling questions examiners ask is about inclusion and exclusion criteria — the characteristics that determined who was eligible to participate in your study and who was not. “Can you explain the criteria you used to select participants?” tests whether your sampling decision was principled and documented rather than informal and convenient.
Prepare to state your inclusion criteria precisely: the specific characteristics that participants had to possess to be eligible. For a study of part-time doctoral students at Malaysian public universities, this might include: enrolled in a doctoral programme at a Malaysian public university at the time of data collection, studying part-time as defined by registration status, having completed at least one academic year of the programme. State also your exclusion criteria: the characteristics that made otherwise eligible participants ineligible — for example, doctoral candidates who had previously withdrawn and re-enrolled, or those who were international students on full-time visas despite part-time registration.
The ability to state these criteria precisely and to explain the rationale for each demonstrates that your sampling was planned and systematic rather than opportunistic. It also demonstrates the kind of methodological transparency that research ethics and scholarly rigour require.
Defending Convenience Sampling When You Used It
Many Malaysian postgraduate students use convenience sampling — selecting participants from accessible populations rather than through rigorous probability or purposive procedures — and many feel uncomfortable defending this in the viva because they know it is methodologically less rigorous than alternatives. Preparing for viva questions about sampling strategy when you used convenience sampling means having an honest defence ready that acknowledges the limitation without catastrophising it.
The honest defence of convenience sampling acknowledges: the practical and ethical constraints that made probability sampling impossible in your context; the steps you took to maximise the diversity of your convenience sample to reduce systematic bias; and what the use of convenience sampling means for the generalisability of your findings — specifically, that the findings apply to the sampled population rather than the broader target population. “The use of a convenience sample limits statistical generalisability, and I have been careful in the discussion not to make claims that go beyond the sampled population. The findings nevertheless provide valuable insights into this specific context that are consistent with patterns documented in adjacent research.” This defence is honest, specific, and appropriately calibrated.
Connecting Sampling to Your Epistemological Position
The most sophisticated responses to sampling questions connect the sampling decision to the broader epistemological position of the study. If your study is positivist and aims to test hypotheses about population-level relationships, probability sampling is the epistemologically aligned choice. If your study is interpretivist and aims to understand the subjective experience of a specific group, purposive sampling that selects participants with relevant lived experience is the epistemologically aligned choice. Being able to articulate this alignment explicitly — “I chose purposive sampling because my interpretivist framework prioritises depth of understanding over breadth of coverage, and probability sampling would have produced participants without the specific experience I needed to investigate” — demonstrates the kind of methodological self-awareness that distinguishes a genuinely competent researcher from one who followed a procedure without fully understanding its rationale.
Preparing for viva questions about your sampling strategy means rehearsing these connections out loud before the examination. Write out a two-minute explanation of your sampling strategy, including the method, the rationale, the criteria, the size determination logic, and the implications for your claims. Practice it until you can deliver it fluently and confidently. That fluency under examination conditions is what transforms sound methodological thinking into an impressive viva performance.
