Start With the Evidence Stage
| Stage | What it can help examine | Important boundary |
|---|---|---|
| In vitro | Behavior in cells, isolated systems, or laboratory assays. | An assay result does not establish what happens in a whole organism. |
| Animal or preclinical | Mechanisms, model-specific outcomes, and questions for later study. | Findings may not translate to humans or other species. |
| Observational human research | Patterns or associations in measured populations. | Association alone does not establish causation. |
| Controlled clinical research | Defined outcomes under a protocol with specified participants and comparators. | One study does not erase limitations or replace the full evidence base. |
| Regulatory review | A regulator's review for a specific product, indication, population, and labeling. | Research discussion is not the same as regulatory approval. |
Review the Study Before the Headline
Question and model
What precise question was asked, and does the experimental model match the claim being discussed?
Controls and comparison
Was there an appropriate control or comparator, and were groups handled consistently?
Sample and exclusions
How was sample size chosen, and were exclusions, missing observations, or early stopping explained?
Methods and materials
Are the material identity, methods, conditions, and analysis described well enough to understand or reproduce the work?
Outcomes and statistics
Were outcomes defined in advance, and do the reported estimates and uncertainty support the written conclusion?
Funding and conflicts
Who funded the work, what interests were disclosed, and are the data or protocol available for review?
Separate Observation, Interpretation, and Claim
- Observation: what the researchers directly measured under the stated conditions.
- Interpretation: what the authors think the observations may mean.
- Claim: the broader statement repeated in an abstract, headline, product page, or discussion.
- Evidence boundary: the populations, models, doses, methods, and outcomes the study did not test.
A careful summary keeps these layers separate. It also records null findings, contradictory evidence, uncertainty, corrections, and retractions rather than selecting only favorable language.
Rigor, Replication, and the Larger Evidence Base
NIH describes scientific rigor in terms of unbiased and well-controlled design, methodology, analysis, interpretation, and reporting. Reproducibility and independent replication matter because a single result can change when methods, samples, models, or analytical choices change. Strong conclusions normally depend on the accumulated evidence, not one paper in isolation.