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Facts, Summary & Definition

  • Accuracy is a measurement of how close a measured value is to the true value
  • Precision is a measurement of how close two or more measurements are to each other
  • Accuracy and precision are not the same!

What is accuracy?

In science, accuracy refers to how close the measured value is to a known value. For example, if you weigh a packet of sugar and obtain a reading of 500g but you know the packet weight 590g, then your measurement was not accurate as it is not close to the known value.

Accuracy is not the same as precision.

What is precision?

In science, precision refers to how close two or more measurements are to each other. If we use the same example of the bag of sugar above: you may obtain a measurement of 500g five times. In this case, your measurement was precise but not accurate – this is because your measured values were close to each other, but not to the known measurement.

High accuracy, high precision!

In science, we always aim for high accuracy and high precision. This is explained well by the figure below.

It is useful to think of the bullseye as the standard or known measurement!

Further Reading