7
In a laboratory using a standard solution of the parameter and a representative lot of reagent (for
each parameter) the following standard deviations were obtained:
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.
PRECISION AND ACCURACY
Parameter
Standard Solution Standard Deviation
Hardness LR 150 mg/L
10 mg/L
Hardness MR 350 mg/L
15 mg/L
Hardness HR 520 mg/L
20 mg/L