7
Precision
is how closely repeated measurements
agree with each other. Precision is usually
expressed as standard deviation (SD).
Accuracy
is defined as the nearness of a test
result to the true value.
Although good precision suggests good accuracy,
precise results can be inaccurate. The figure
explains these definitions.
In a laboratory using a standard solution of 2.00
mg/L bromine and a representative lot of reagent,
an operator obtained with a single instrument a
standard deviation of 0.06 mg/L.
PRECISION AND ACCURACY