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Study designs, ranked by what they can actually prove
Study designs, ranked by what they can actually prove: this guide has a section for each design — randomised trial, crossover, cluster, pragmatic trial…
This launch guide maps the topic, the source base and the practical questions. Check the linked official authority before acting on a rule, deadline, price or safety requirement.
What this guide covers
This guide has a section for each design — randomised trial, crossover, cluster, pragmatic trial, prospective and retrospective cohort, case-control, cross-sectional, ecological, case report, n-of-1, animal, cell culture, Mendelian randomisation, registry study and before-after — saying what question it can answer, its classic failure mode, and one famous result that fell over because the design could not carry it.
A chooser at the top asks what you want to know and names the design that would answer it, which is the part students and journalists link to. Eighteen pages.
How to use it
Use Study designs, ranked by what they can actually prove as a structured learning path: begin with the vocabulary, follow the evidence map, and keep the uncertainty labels attached to claims as you compare sources.
The page keeps the main question, its evidence base and its limits together in one canonical place. That makes it useful as a quick orientation and avoids splitting a broad subject into shallow pages before each narrower answer has enough verified material of its own.
Search vocabulary in four languages
Terminology changes across borders. These are example phrases people use for the same subject in Estonian, Finnish, Russian and English; they are included as a practical vocabulary aid, not as hidden keywords.
| Language | Example phrase |
|---|---|
| Estonian | uuringu tüübid teaduses |
| Finnish | tutkimusasetelmat vertailu |
| Russian | виды научных исследований иерархия |
| English | hierarchy of evidence explained |
Evidence and provenance
The evidence map below records the primary, official or openly licensed material chosen for this guide. It is deliberately visible so a reader can tell the difference between a rule published by an authority, a measured dataset and an editorial explanation.
Source: own writing; the OCEBM Levels of Evidence 2011 (free) and the Cochrane Handbook cited. · checked 2026-09-09
Source names are preserved even where an authority changes its web address. No figure is added to this launch page unless it is already present in the cited source description or can be computed from a named dataset.
Scope and boundaries
This guide owns the explanatory layer for the topic. Personal decisions, diagnoses, legal determinations and live availability remain with the relevant professional or official service.
Connected TempoLife guides
The following paths are the intentional hand-offs named in the brief. They keep adjacent subjects separate while making the next useful reference easy to find.
Research
Continue to the related TempoLife reference.
Myths
Continue to the related TempoLife reference.
Why it belongs on TempoLife
/research, /myths.
Frequently asked questions
What does this guide cover?
This guide has a section for each design — randomised trial, crossover, cluster, pragmatic trial, prospective and retrospective cohort, case-control, cross-sectional, ecological, case report, n-of-1, animal, cell culture, Mendelian randomisation, registry study and before-after — saying what question it can answer, its classic failure mode, and one famous result that fell over because the design could not carry it. A chooser at the top asks what you want to know and names the design that would answer it, which is…
What evidence does it use?
own writing; the OCEBM Levels of Evidence 2011 (free) and the Cochrane Handbook cited.
Where does this guide stop?
It explains the topic and points to primary or official sources. It does not replace a qualified professional, an official decision, or advice based on your own circumstances.
Turn the reference into a routine
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