THE SHORT ANSWER
A fact is a claim that can be checked against evidence. An opinion expresses a judgment or preference. An assumption is treated as true for the purpose of reasoning. An inference is a conclusion drawn from evidence, while an interpretation explains what that evidence means.
Use labels to expose the reasoning
| Type | Meaning | Example |
|---|---|---|
| Fact claim | Checkable against evidence | Forty people completed the survey |
| Opinion | A value judgment or preference | The form is too long |
| Assumption | Accepted provisionally | Respondents understood every question |
| Inference | Conclusion drawn from observations | Shorter forms may improve completion |
| Interpretation | Account of what the observations mean | The drop suggests avoidable friction |
A fact claim still needs scope and evidence
‘Sales rose’ is checkable, but incomplete. Which sales measure, compared with what period, in which market, and from which record? A true number can support a misleading impression when its scope is hidden.
Calling something a fact does not make it correct. The useful distinction is whether it can be tested and what evidence currently supports it.
Trace the move from observation to action
A dashboard shows fewer completed checkouts. The team interprets this as friction, infers that a recent change contributed, assumes tracking remained stable and decides to investigate the changed step. Each move can be reasonable, but each is a different claim.
Annotate a decision note
- Underline checkable factual claims.
- Circle judgments and preferences.
- Write assumptions in the margin.
- Add the evidence behind each inference.
- Mark conclusions that remain interpretations rather than established causes.
Sources & further reading
- Reproducibility and Replicability in Science
National Academies of Sciences, Engineering, and Medicine. A consensus report on evidence, uncertainty, transparency, reproducibility and replication. Scientific standards need proportionate adaptation outside research settings.
- The Green Book 2026
HM Treasury and Government Finance Function. Current official guidance on objectives, options, evidence, risk, uncertainty, appraisal and evaluation. It is designed for public decisions, while the general reasoning principles are adapted here.
Examples and exercises are illustrative unless attributed to a source. No independent expert review is claimed.
A correction, a counterexample or an experience worth sharing?
Join the conversation ↗