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Encyclopedia of Electrical Engineering
 realnfo.com
Encyclopedia of Electrical Engineering

# Accuracy and Precision

Accuracy refers to the closeness of a measured value to a standard or known value.
For example, if in lab you obtain a weight measurement of 3.2 kg for a given substance, but the actual or known weight is 10 kg, then your measurement is not accurate. In this case, your measurement is not close to the known value. If your resulted value are close to 10kg, e.g (9kg or 11kg) then we can say that your measurement is accurate to $\pm1kg$.
Precision refers to the closeness of two or more measurements to each other.
Using the example above, if you weigh a given substance five times, and get 3.2 kg each time, then your measurement is very precise. Precision is independent of accuracy. You can be very precise but inaccurate, as described above. You can also be accurate but imprecise.
For example, if on average, your measurements for a given substance are close to the known value, but the measurements are far from each other, then you have accuracy without precision.