Accuracy
Definition
How close a measured value sits to the true one. It is established against a reference standard, and it is independent of precision: a method can repeat the same wrong answer all day.
In more detail
Accuracy is agreement with the true value and is established against a reference standard of known content. It is independent of precision, and the two are confused often enough that the distinction is worth keeping sharp: a method with a systematic bias repeats the same wrong answer with excellent precision.
Because bias is systematic, repeating a measurement does not reveal it. It is found by measuring something whose value is already known, which is what a reference standard is for and what metrological traceability chains together.
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Entries whose definition mentions Accuracy.
What this means for research sourcing
Purity and identity verification are central to research reproducibility. Every Volta compound ships with >99% HPLC-verified purity and a certificate of analysis.
Related Terms in Quality
Precision
How close repeated measurements of the same sample fall to each other, reported as a relative standard deviation. Repeatability is precision within one run, intermediate precision across days and analysts in one laboratory.
Reproducibility
Agreement between results for the same material measured in different laboratories. It is the widest form of precision and the one that matters when a buyer sends a vial for independent testing.
Calibration
Relating an instrument's signal to known quantities of a reference standard, so a peak area can be read as a concentration. An uncalibrated instrument still produces numbers; they just do not mean anything outside that run.
Method Validation
The documented exercise proving a method does what it claims: specificity, linearity, accuracy, precision, range, and the limits at which it stops working. Validation is done once for the method, not once per sample.
Method Verification
Demonstrating that an already-validated method performs as expected in the laboratory now using it. A compendial method arrives validated; a laboratory still has to show its own instruments and analysts reproduce it.
System Suitability
Checks run immediately before samples to prove the instrument is fit to measure anything that day: peak shape, resolution between critical pairs, and repeatability of replicate injections. A failed system suitability invalidates the run rather than the material.
Analytical Selectivity
A method's ability to measure the intended analyte without interference from impurities, excipients or degradation products. A purity figure from a method that cannot separate a close-eluting impurity overstates purity.
Orthogonal Method
A second method resting on a different physical principle, used to test a result rather than repeat it. Running reversed-phase HPLC and then mass spectrometry is orthogonal; running the same HPLC method twice is not.