The overall quality of a result, judged by how little it misses the measurand's true value once both scatter and offset are counted. In strict metrology usage accuracy is qualitative, so a result is described as more or less accurate, while the quantitative statement is the uncertainty or the error. Instrument data sheets use the word loosely to mean the manufacturer's specification limits, such as ±(0.02 % of reading + 2 counts).
Data sheet says accuracy 0.05 percent, but that's a one-year spec at 23 plus or minus 5 degrees, not an uncertainty.
In a metrology meeting, quoting 'the accuracy' as a number marks you as a datasheet reader; quote the uncertainty or the spec instead.
Also heard as
- measurement accuracy
Do not mix it up with
- Precision: Precision is tight grouping of repeated readings; accuracy is closeness to the true value, and a precise instrument can still be inaccurate.
Related terms
Precision
How well repeat readings of the same item agree with one another, with no reference to whether they are right.
Trueness
Where a method's long-run average result lands relative to a reference value; small bias means good trueness.
Uncertainty
A number that states how much doubt surrounds a measured value, as a standard deviation or as a stated interval.
Spec
Shop clipping for a manufacturer's accuracy specification, the published limits an instrument should stay within.