Research reference · 23 connected terms

Research evidence glossary: connect the terms before judging a claim.

A result can sound convincing while its molecular identity, study design, statistical scale, or measurement assumptions remain unclear. This glossary gives each term a plain-language boundary and connects it to a complete, source-linked reading path.

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Published by PeptideSchool Editorial Desk · Published and reviewed August 11, 2026

Educational content only. Not medical advice.

4 definitions

Molecular identity

Terms that establish what molecule or molecular record a source is actually describing.

Peptide: A molecule built from amino acids joined by peptide bonds. Scientific usage does not rely on one universal length cutoff: sequence, structure, folding, function, biosynthesis, and field convention can all affect whether a molecule is called a peptide or a protein.
Protein: One or more polypeptide chains considered together with their structure and biological function. Length alone does not settle every peptide-versus-protein label, so the source's definition and molecular record matter when comparing studies.
Sequence identity: The exact order of residues plus any terminal changes, substitutions, conjugations, or other defined modifications. Two familiar labels are not enough to prove that two study materials represent the same molecular entity.
Alias and nomenclature: An alias is an alternative label used for a molecule, development program, or record. Treat aliases as a research lead, then reconcile sequence, modifications, sponsor records, and authoritative databases before combining evidence under one identity.

4 definitions

Evidence maturity

Terms that separate biological plausibility, human observation, and comparative inference.

Preclinical evidence: Evidence from laboratory systems, cells, tissues, computational models, or nonhuman animals. It can clarify mechanisms and generate hypotheses, but it does not by itself establish safety, effectiveness, or an expected outcome in people.
Clinical evidence: Evidence generated from research involving people. The label is broad: interpretation still depends on study phase, population, comparator, allocation, outcome definitions, follow-up, missing data, and risk of bias.
Observational study: A study in which investigators observe exposures and outcomes without randomly assigning the exposure. Observational data can identify associations and patterns, while confounding, selection, measurement, and reverse-causation questions remain central.
Randomized controlled trial: An interventional study that uses a random allocation process to assign participants to comparison groups. Randomization can reduce systematic baseline differences on average, but allocation concealment, missing data, outcome reporting, adherence, and analysis still determine credibility.

5 definitions

Design and synthesis

Terms that show how a question was framed, measured, protected from bias, and combined with other studies.

Primary endpoint: The main prespecified outcome used to answer the central study question. A primary endpoint should be interpreted with its exact definition, time point, analysis population, missing-data method, and any changes made after registration or protocol publication.
Randomization: A chance-based assignment process intended to make comparison groups exchangeable at baseline. A credible report explains how the sequence was generated, how allocation was concealed, and whether the analysis preserved the assigned comparison.
Bias, confounding, and effect modification: Bias is systematic error introduced by design, conduct, measurement, analysis, or reporting. Confounding mixes an exposure-outcome relationship with another factor. Effect modification is a real difference in an effect across defined groups or contexts, not automatically an error.
Systematic review: A review that uses explicit, reproducible methods to define a question, search for studies, select records, assess limitations, and synthesize findings. A transparent method distinguishes it from an informal narrative selection of favorable papers.
Meta-analysis: A statistical combination of results from multiple studies. The pooled estimate inherits the eligibility choices, outcome definitions, bias, heterogeneity, and publication pattern of its inputs; pooling alone does not make unlike studies comparable.

5 definitions

Statistical interpretation

Terms that describe the size, uncertainty, compatibility, and framing of a reported result.

Mean, median, and standard deviation: The mean is an arithmetic average, the median is the middle ordered value, and the standard deviation summarizes spread around the mean. None of these alone reveals the full distribution, outliers, missingness, or whether the summary fits the data shape.
Effect size: A quantitative estimate of how large a difference or association is on a specified scale. Its practical meaning depends on the outcome, units, baseline risk, study design, and uncertainty, not only on whether a threshold test was passed.
Confidence interval: An interval produced by a statistical procedure to express uncertainty around an estimate. It should be read with the point estimate, scale, assumptions, sample, and repeated-sampling interpretation; it is not a probability statement that the true value lies inside this one realized interval.
P-value and statistical significance: A p-value measures how incompatible the observed data are with a specified statistical model, assuming that model and null hypothesis. It does not measure effect size, importance, replication probability, study quality, or the probability that the hypothesis is true.
Relative risk, absolute risk, and odds ratio: Relative risk compares probabilities, absolute risk keeps the outcome frequency on its original scale, and an odds ratio compares odds rather than probabilities. They can produce very different impressions, especially when the underlying event is uncommon or baseline risks differ.

5 definitions

Measurement and reproducibility

Terms that keep quantities, units, transformations, and reported precision auditable.

Mass concentration: Mass of a specified substance divided by solution volume, expressed with compatible mass-per-volume units. It is not interchangeable with molarity unless the molecular identity and molar mass needed for conversion are known.
Molarity: Amount of substance in moles divided by solution volume. Moving between molarity and mass concentration requires a defined molecular entity and its molar mass; a product label or informal alias may not provide enough information.
Dilution factor: The ratio describing how concentration changes after a defined dilution step. Stepwise dilution factors multiply, but the arithmetic remains credible only when final volume, transfer volume, units, mixing, and measurement assumptions are explicit.
Measurement uncertainty: A quantified expression of doubt associated with a measured or derived value. It can include instrument resolution, calibration, repeatability, environmental effects, sampling, and model assumptions; calculation precision cannot recover information that the inputs never contained.
Significant figures: A reporting convention that communicates the meaningful precision of a value. Extra calculator digits do not automatically become evidence; rounding should follow the least informative input and the uncertainty appropriate to the measurement process.

Source framework

Definitions are anchors, not substitutes for methods.

The glossary summarizes stable research concepts and links to deeper PeptideSchool explainers. Those explainers preserve the study-design and source context that a short definition cannot. Always verify how the original record defines its molecule, population, outcome, model, and statistical scale.

Peptides: MeSHNational Library of MedicineControlled vocabulary for peptide terminology and hierarchy.ClinicalTrials.gov Glossary TermsU.S. National Library of MedicineOfficial definitions for study types, allocation, phases, and outcomes.CONSORT 2025 StatementCONSORT GroupPrimary reporting guidance for randomized trials.PRISMA 2020 StatementPRISMA GroupPrimary reporting guidance for systematic reviews.ASA Statement on P-ValuesAmerican Statistical AssociationConsensus principles for interpreting p-values responsibly.NIST Technical Note 1297National Institute of Standards and TechnologyOfficial guidance for evaluating and expressing measurement uncertainty.The International System of UnitsBureau International des Poids et MesuresInternational reference for quantities, units, and coherent equations.

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