Study Design Flowchart
Answer a few questions about your research question and the tool recommends the right study design — with strengths, limitations, and examples.
Study design hierarchy
The evidence pyramid ranks study designs by their ability to minimise bias. Higher designs provide stronger causal evidence but require more resources.
| Level | Design | Causal inference | Best for | Key measure |
|---|---|---|---|---|
| 1 | Systematic Review / Meta-Analysis | Highest | Summarising all evidence on a question | Pooled OR, RR, MD |
| 2 | Randomised Controlled Trial (RCT) | Very high | Evaluating treatment or intervention efficacy | RR, ARR, NNT |
| 3 | Cohort Study | Moderate–high | Incidence, risk factors, natural history | RR, Incidence Rate |
| 4 | Case-Control Study | Moderate | Rare diseases, multiple exposures | Odds Ratio |
| 5 | Cross-Sectional Study | Low | Prevalence, associations at a point in time | Prevalence, PR |
| 6 | Ecological Study | Very low | Population-level associations, hypothesis generation | Correlation |
| 7 | Case Report / Case Series | None | Rare conditions, adverse events, novel observations | Descriptive |
Source: Sackett DL et al. Evidence Based Medicine. Churchill Livingstone, 1997. Reviewed Sep 2026.
For educational and research planning purposes. Study design selection in practice depends on many contextual factors including ethics, feasibility, funding, and local context. Consult a research methodologist for complex study designs.