Accuracy and Precision

Accuracy and precision are words used interchangeably in normal language. They have a key difference in physics.

Accuracy is defined as how close a result is to the accepted or standard value.

Precision is defined as how close together multiple repeated results are.

In this example, some of the data sets are more useful than others.

Points on the target that are on average far away from the center point are affected by a systematic error. This determines the accuracy. This could come from a constant crosswind, for example.

Points on the target that are spread far apart are affected by a random error. This determines the precision. This could come from tremors in the shooter's hands, for example.

What we really want is data that is both precise and accurate. This would have the lowest uncertainty!

The trouble with this is that the most precise and accurate tools are often expensive and inappropriate for small-scale use. We wouldn't measure someone's height with a powerful electron microscope unless it was absolutely vital to know their height accurately and precisely. It is up to you as a scientist to be wise in your experimental design, and choose the right tools for the job!