Different Types of Medical Research Explained
Medical research types differ mainly in the kind of question they answer: how common is something, what causes it, does an intervention work, how accurate is a test, what does a body of evidence conclude, or how do people experience care.
Overview table
| Type | Typical question | Examples |
|---|---|---|
| Descriptive | How often, in whom? | Case report, case series, cross-sectional survey |
| Analytical observational | What is associated with an outcome? | Cohort, case-control |
| Experimental | Does an intervention work? | Randomised controlled trial |
| Diagnostic accuracy | How well does a test classify? | Sensitivity/specificity study |
| Evidence synthesis | What does all the evidence say? | Systematic review, meta-analysis, scoping review |
| Qualitative | How do people experience or explain this? | Interviews, focus groups |
| Basic science | How does biology work? | Cell, animal and mechanistic studies |
How to match question to type
- Frequency or burden: cross-sectional or registry-based studies.
- Cause or risk factor: cohort studies (case-control when the outcome is rare).
- Treatment effects: randomised trials where feasible and ethical.
- Test performance: diagnostic accuracy studies compared with a reference standard.
- Summary of existing evidence: systematic review.
Illustrative example
Invented for teaching. A single clinical topic, asthma in children, produces several kinds of research: a cross-sectional survey of school absence, a cohort study of early-life antibiotics and later asthma, a randomised trial of an inhaler technique programme, and a systematic review of school-based interventions.
Common pitfalls
- Using a design that cannot answer the question, such as claiming causation from a cross-sectional survey.
- Calling any literature summary a "systematic review" without a protocol and reproducible search.
Key takeaways
- Choose the type by the question, not by convenience.
- Higher "evidence levels" help only when the design suits the question.
References and further reading
- Hulley SB, Cummings SR, Browner WS, Grady D, Newman TB. Designing Clinical Research. 4th ed. Lippincott Williams & Wilkins; 2013. Link
- EQUATOR Network: Enhancing the QUAlity and Transparency Of health Research (reporting guideline library). Link
- Higgins JPT, Thomas J, Chandler J, et al., editors. Cochrane Handbook for Systematic Reviews of Interventions. Cochrane. Link
Related reading
This page is general educational information about research methods. It is not medical, legal or regulatory advice; follow your institution's ethics board and your target journal's instructions.