Direct comparison
Validity vs. Accuracy: Key Differences
Validity vs accuracy: accuracy is closeness to a true value (VIM), validity is whether a measure captures its construct (COSMIN). Side-by-side table.
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How do Accuracy, Validity compare side by side?
The table below compares Accuracy, Validity across 9 procurement-relevant dimensions, from the question it answers through source.
Side-by-side comparison
| Dimension | Accuracy | Validity |
|---|---|---|
| The question it answers | Accuracy asks how close a measured value is to the true value of the quantity being measured. The VIM defines it as the “closeness of agreement between a measured quantity value and a true quantity value of a measurand.” | Validity asks whether an outcome measure measures the construct it purports to measure. COSMIN defines the validity domain as “the degree to which an outcome measure measures the construct it purports to measure.” |
| What it is measured against | A true or reference quantity value of a defined measurand. | A construct, such as a symptom, ability or attitude, that the instrument is supposed to capture. |
| Is it a number? | No. The VIM notes accuracy “is not a quantity and is not given a numerical quantity value.” A measurement is called more accurate when it offers a smaller measurement error. | Described as a degree, supported by evidence of different kinds rather than by one error figure. |
| Kinds of evidence | Comparison with a reference value, and the size of the error. The VIM links accuracy to two other concepts: trueness (systematic error) and precision (random error). | COSMIN lists content validity (including face validity), construct validity (structural validity, hypotheses testing, cross-cultural validity or measurement invariance) and criterion validity. |
| Where error fits | Central. Trueness is inversely related to systematic error and is not related to random error; precision describes how closely replicate measurements agree. | Measurement error is a separate matter. In the COSMIN taxonomy it belongs to the reliability domain, which is distinct from the validity domain. |
| Content requirement | None beyond a well-defined measurand and a reference value to compare against. | For content validity, the content must be “relevant, comprehensive, and comprehensible with respect to the construct of interest and target population.” |
| Terminology trap | The VIM says “accuracy” should not be used for trueness, and that “precision” is erroneously used to mean accuracy. The three terms are related but not interchangeable. | Validity is not a synonym for accuracy. It is split into subtypes, and each subtype needs its own evidence. |
| Which one to reach for | Use accuracy (with trueness and precision) when the task is to describe how far readings of a defined quantity sit from a reference value. | Use validity when the task is to judge whether an instrument or score captures the intended construct, and name the subtype (content, construct or criterion) you have evidence for. |
| Source | JCGM 200:2012, International Vocabulary of Metrology (VIM, 3rd edition), clauses 2.13 to 2.15, bipm.org, read 2026-10-29. | COSMIN taxonomy of measurement properties, cosmin.nl, read 2026-10-29. |
Common questions
Common questions about Accuracy vs Validity
Is validity the same as accuracy?
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No. Accuracy, as the VIM defines it, is closeness of agreement between a measured value and a true value of a measurand, and it is a qualitative concept rather than a number. Validity, as COSMIN defines it, is the degree to which an outcome measure measures the construct it purports to measure. One compares readings with a true or reference value; the other asks whether the right construct is being captured.
Can a measurement be accurate but not valid?
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The two terms answer different questions, so meeting one does not settle the other. Accuracy is judged against a measurand’s true value; validity is judged against the construct the measure is meant to represent. When the quantity read off an instrument is not the construct of interest, small measurement error does not make the score a valid measure of that construct.
What is the difference between validity and accuracy in one sentence?
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Accuracy is about how close a measured value is to the true value of what was measured; validity is about whether what was measured is the construct you meant to measure.
How is accuracy different from precision and trueness?
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The VIM defines trueness as closeness of agreement between the average of an infinite number of replicate measured values and a reference value, related to systematic error. Precision is closeness of agreement between replicate measurements under specified conditions, related to random error. Accuracy is related to both, and the VIM advises against using one term for another.
Going deeper
