[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Epidemiology](https://durgical.com/en/epidemiology/) › Study designs # Study designs Descriptive, case-control, cohort, cross-sectional, ecological studies and clinical trials. 30 pages ## Concept - [**Blinding** Hiding who receives which treatment, so that the expectations of patient, doctor or assessor do…](https://durgical.com/en/epidemiology/blinding/) - [**Intention-to-treat analysis** Each patient is analysed in the group chance assigned them to, even if they never received or…](https://durgical.com/en/epidemiology/intention-to-treat-analysis/) - [**Interim analyses and early stopping** Looking at a trial's data before it ends lets it stop for clear benefit, harm or futility, but…](https://durgical.com/en/epidemiology/interim-analyses-and-early-stopping/) - [**Matching** Choosing controls who resemble the cases in age, sex or another factor, so that factor cannot…](https://durgical.com/en/epidemiology/matching/) - [**Phases of clinical trials** A new medicine moves through phases: safety in a few volunteers first, then efficacy in…](https://durgical.com/en/epidemiology/phases-of-clinical-trials/) - [**Pragmatic and explanatory trials** An explanatory trial asks whether something can work under ideal conditions; a pragmatic one…](https://durgical.com/en/epidemiology/pragmatic-and-explanatory-trials/) - [**Randomisation and allocation concealment** Chance draws up the list of who goes to each group; concealment stops anyone from seeing it…](https://durgical.com/en/epidemiology/randomisation-and-allocation-concealment/) - [**Real-world evidence and comparative effectiveness** Uses data from everyday care (registries, health records, billing) to see how treatments perform…](https://durgical.com/en/epidemiology/real-world-evidence-and-comparative-effectiveness/) - [**Study designs: how to tell them apart** Three questions name almost any design: who assigned the exposure, is there a comparison group…](https://durgical.com/en/epidemiology/study-designs-how-to-tell-them-apart/) ## Study design - [**Case report and case series** One or several patients with something new or rare are described in detail](https://durgical.com/en/epidemiology/case-report-and-case-series/) - [**Case-cohort study** Inside a large cohort, all cases plus a random subcohort chosen at the start are analysed; the…](https://durgical.com/en/epidemiology/case-cohort-study/) - [**Case-control study** Start with sick people (cases) and healthy people (controls) and compare how many were exposed…](https://durgical.com/en/epidemiology/case-control-study/) - [**Case-crossover design** Only cases are studied: each person is compared with themselves, just before the event and at…](https://durgical.com/en/epidemiology/case-crossover-design/) - [**Cluster randomised trial** Whole groups (schools, clinics, neighbourhoods) are randomised instead of people, because the…](https://durgical.com/en/epidemiology/cluster-randomised-trial/) - [**Cohort study** Exposed and unexposed people are followed over time and investigators count who falls ill](https://durgical.com/en/epidemiology/cohort-study/) - [**Community trial** A prevention programme is tested in whole communities (towns, neighbourhoods) and compared with…](https://durgical.com/en/epidemiology/community-trial/) - [**Cross-sectional study** A snapshot: exposure and disease are measured at the same time in a sample](https://durgical.com/en/epidemiology/cross-sectional-study/) - [**Crossover trial** Each patient gets both treatments, one after the other in random order: they are their own…](https://durgical.com/en/epidemiology/crossover-trial/) - [**Ecological study** It compares whole groups (municipalities, countries, years), not people](https://durgical.com/en/epidemiology/ecological-study/) - [**Factorial trial** One trial answers two questions: two interventions are randomised at once, alone, together or…](https://durgical.com/en/epidemiology/factorial-trial/) - [**Family, twin and adoption studies** To weigh the role of genes, researchers compare relatives, identical with fraternal twins, and…](https://durgical.com/en/epidemiology/family-twin-and-adoption-studies/) - [**Linkage and genetic association studies (GWAS)** They look for the region or variant of the genome that travels with a disease: in families…](https://durgical.com/en/epidemiology/linkage-and-genetic-association-studies/) - [**Migrant studies** If people who move take on the rates of their new country, the cause lies mostly in the…](https://durgical.com/en/epidemiology/migrant-studies/) - [**N-of-1 trial** A trial in a single patient: two treatments alternate several times, in random order, to find…](https://durgical.com/en/epidemiology/n-of-1-trial/) - [**Nested case-control study** Inside a cohort that is already followed, those who fall ill and a few controls are picked, and…](https://durgical.com/en/epidemiology/nested-case-control-study/) - [**Quasi-experimental designs** They evaluate a programme or policy without randomisation, using comparisons over time or with…](https://durgical.com/en/epidemiology/quasi-experimental-designs/) - [**Randomised controlled trial** Chance decides who gets the intervention and who gets the control](https://durgical.com/en/epidemiology/randomised-controlled-trial/) - [**Superiority, equivalence and non-inferiority trials** A better treatment is not always the goal: sometimes it is enough to show that a simpler or…](https://durgical.com/en/epidemiology/superiority-equivalence-and-non-inferiority-trials/) - [**Uncontrolled studies and historical controls** Comparing today's patients with past ones, or with themselves before treatment, tends to…](https://durgical.com/en/epidemiology/uncontrolled-studies-and-historical-controls/) ## Measure - [**Vaccine efficacy and evaluating preventive measures** Vaccine efficacy is the percentage by which a vaccine lowers the risk of disease in vaccinated…](https://durgical.com/en/epidemiology/vaccine-efficacy-and-evaluating-preventive-measures/) ## A to Z - [A](https://durgical.com/en/epidemiology/a-z/a/) - [B](https://durgical.com/en/epidemiology/a-z/b/) - [C](https://durgical.com/en/epidemiology/a-z/c/) - [D](https://durgical.com/en/epidemiology/a-z/d/) - [E](https://durgical.com/en/epidemiology/a-z/e/) - [F](https://durgical.com/en/epidemiology/a-z/f/) - [G](https://durgical.com/en/epidemiology/a-z/g/) - [H](https://durgical.com/en/epidemiology/a-z/h/) - [I](https://durgical.com/en/epidemiology/a-z/i/) - [K](https://durgical.com/en/epidemiology/a-z/k/) - [L](https://durgical.com/en/epidemiology/a-z/l/) - [M](https://durgical.com/en/epidemiology/a-z/m/) - [N](https://durgical.com/en/epidemiology/a-z/n/) - [O](https://durgical.com/en/epidemiology/a-z/o/) - [P](https://durgical.com/en/epidemiology/a-z/p/) - [Q](https://durgical.com/en/epidemiology/a-z/q/) - [R](https://durgical.com/en/epidemiology/a-z/r/) - [S](https://durgical.com/en/epidemiology/a-z/s/) - [T](https://durgical.com/en/epidemiology/a-z/t/) - [U](https://durgical.com/en/epidemiology/a-z/u/) - [V](https://durgical.com/en/epidemiology/a-z/v/) - [W](https://durgical.com/en/epidemiology/a-z/w/) - [Y](https://durgical.com/en/epidemiology/a-z/y/) [← Epidemiology, biostatistics and public health](https://durgical.com/en/epidemiology/) Educational content on epidemiological and statistical methods; the examples use made-up numbers to teach the calculation. Not a clinical or legal guide: current Colombian rules are in the official sources. Representative model, for educational purposes only. --- Source: https://durgical.com/en/epidemiology/areas/designs/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/epidemiology/areas/designs/