Direct comparison
Qualitative vs. Quantitative Research
Compare qualitative and quantitative research: designs, data, sample-size logic, IRB review, and when to use mixed methods.
Side-by-side comparison
| Dimension | Qualitative Research | Quantitative Research |
|---|---|---|
| Core research question | How and why something happens — meaning, context, and lived experience | How much, how many, or whether a measurable relationship exists |
| What it studies | Processes, perceptions, and social/behavioral context — often exploratory or explanatory of a phenomenon | Variables, frequencies, relationships, and effects — testing a hypothesis or estimating a parameter |
| Typical data types | Text (transcripts, field notes, documents), audio/video, images — non-numeric and contextually rich | Numeric — counts, scale scores, lab values, survey responses coded to numbers |
| Common data collection methods | Semi-structured/unstructured interviews, focus groups, participant observation, document/artifact analysis | Structured surveys, validated instruments, physiological/lab measurement, secondary or administrative datasets |
| Common study designs/traditions | Grounded theory, ethnography, phenomenology, case study, narrative inquiry (Creswell & Poth's five approaches) | Randomized controlled trial (RCT), quasi-experimental design, cohort study, cross-sectional survey, correlational/case-control design |
| Typical analysis approach | Coding and thematic analysis, constant comparison, narrative or discourse analysis — iterative, often concurrent with data collection | Descriptive and inferential statistics (regression, ANOVA, t-tests) per a pre-specified analysis plan set before data collection |
| Sample size logic | Determined by data/thematic saturation or "information power," not a formula — a judgment about adequacy | Determined in advance by a statistical power calculation tied to expected effect size and target power |
| Generalizability claim | Transferability — findings are richly described so a reader can judge fit to another context | Statistical generalizability — findings extrapolated to a defined population if the sample is representative |
| Rigor / quality criteria | Trustworthiness (Lincoln & Guba): credibility, transferability, dependability, confirmability | Validity, reliability, and objectivity — internal/external validity, measurement reliability, statistical power |
| Researcher's role | Instrument of data collection; reflexivity and positionality are disclosed as part of the method | Positioned as an external, neutral measurer; researcher effects are controlled for or randomized away |
| Human-subjects / IRB considerations | Same 45 CFR 46 definition applies; interview/observation research often qualifies for exempt (46.104(d)(2)) or expedited review, but protocols must address confidentiality and the emergent, iterative nature of the design | Same 45 CFR 46 definition applies; interventional designs (e.g., RCTs) more often require full-board review given a fixed, pre-specified procedure and analysis plan |
| How it reads in a proposal/protocol | Approach section justifies the tradition chosen, the sampling/saturation strategy, and trustworthiness safeguards — no power calculation | Approach section centers on hypotheses, a pre-specified analysis plan, and a power/sample-size justification |
| When it stands alone vs. needs mixed methods | Sufficient alone when the goal is understanding meaning or process with no need to quantify prevalence or test a hypothesis | Sufficient alone when the goal is measuring magnitude or testing a hypothesis with no need to explain why |
Common questions
FAQ
Is qualitative research less rigorous than quantitative research?+
No — it uses a different rigor framework, not a lesser one. Quantitative research is judged on validity, reliability, and objectivity; qualitative research is judged on trustworthiness (Lincoln & Guba, 1985): credibility, transferability, dependability, and confirmability. Applying quantitative criteria (e.g., expecting a power calculation) to a qualitative protocol is a mismatch, not a rigor gap.
Does IRB review differ for qualitative research versus quantitative research?+
The underlying Common Rule (45 CFR 46) definition of human-subjects research is the same for both. In practice, qualitative interview/focus-group/observation studies often qualify for exempt review under 46.104(d)(2), while quantitative interventional designs such as RCTs more often require full-board review because they involve a fixed, pre-specified procedure. Protocols for emergent qualitative designs should explicitly describe how the interview guide or sampling frame may evolve, and the amendment pathway for that.
What is data saturation, and how is it different from a power calculation?+
Data saturation is the point in qualitative data collection where continued interviews or observations stop surfacing new themes or information — it is a judgment about adequacy made during and after data collection, not a number calculated in advance. A statistical power calculation, used in quantitative research, sets the required sample size before data collection based on an expected effect size and target power level.
When should a study use mixed methods instead of choosing qualitative or quantitative alone?+
When a research question needs both a measurable effect and an explanation of it, or needs exploratory understanding before something can be meaningfully measured. Creswell's typology names three core designs: convergent (qualitative and quantitative data collected in parallel and merged at interpretation), explanatory sequential (quantitative first, qualitative data used to explain the results), and exploratory sequential (qualitative first, used to build an instrument or hypothesis that quantitative data then tests).
Can qualitative research findings be generalized?+
Not in the statistical sense. Qualitative research aims for transferability — findings are described in enough contextual detail that a reader can judge whether they plausibly apply to another setting. That judgment is made by the reader, not extrapolated by the researcher the way a representative quantitative sample is generalized to a population.
Going deeper
