Units of Measure


Accuracy refers to how closely a measured value agrees with the correct or target value.
Precision refers to how closely individual measurements agree with each other and reflects a repeatability in those measurements.

High accuracy Low precision
This illustrates accuracy. Measurements are on target.
High precision Low accuracy
This illustrates precision. Measurements are very close to each other and repeatable.

This illustrates Accuracy AND Precision. Each measurement is on target and also highly repeatable.

Instruments have a finite amount of accuracy and it is important to report measurements within that level of accuracy. Significant figures,  report the number of digits that are known to some degree of confidence with the measuring device. With increased sensitivity of the equipment , the number of significant figures increases.