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Summary

Precision and Accuracy

• Accuracy indicates how close the measurement is to the true/actual value.

• Precision indicates how consistent a measurement is.

• The degree of precision is determined by the smallest increment on the scale of the measuring tool.

• A measuring tool can be
• both accurate and precise
• accurate but not precise
• precise but not accurate

• A precise but inaccurate tool needs to be calibrated.

• Choosing the measurement tool with the amount of precision required by the application is important.

Uncertainty

• Uncertainty indicates the margin of error of a measurement.

• If unstated, uncertainty is half the precision of the measuring tool.
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• Uncertainty is written as ± value at the end of the measurement.

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