Definition
Precision
Precision describes how finely a result is stated or how closely repeated measurements agree.
What it means
Precision can mean a tool reads in smaller steps, such as millimetres instead of centimetres. It can also mean repeated measurements bunch closely together. Extra decimal places do not create real precision unless the tool and method support them.
Remember it
Precision asks: how fine are the steps, or how tightly do repeats bunch?
Example
One ruler is marked every centimetre; another is marked every millimetre. The millimetre ruler allows finer readings. If three readings are 10.2, 10.2, and 10.3 cm, they are close together, so the set is precise—even if the accepted length is 11.0 cm.
Watch for
A precise result may still be inaccurate, and a rounded result can be accurate enough for its purpose.
Common mix-up
Accuracy is closeness to the accepted value; precision is fineness or repeat agreement.
Exact meaning
Precision describes either the fineness or resolution of a measurement or reporting scale, or the closeness of agreement among repeated measurements made under stated conditions; precision alone does not show closeness to the true or accepted value.