Precision and Accuracy

Measurements are an important part of doing experiments. Two different and often confused concepts pertaining to measurements are accuracy and precision.

Accuracy is how close to "true" measurements are. Measuring devices or techniques can easily be inaccurate and lead to false measurements, and no matter how accurate a device may be, there is still a tolerance for error. No measurement is perfect. Accuracy must be accounted for in your results.

Precision is how consistent your results are for the same phenomena over several measurements, or how repeatable a device's (like a spring's) performance can be made. Precision as a measure of variation, must be accounted for in your calculations and results.

The dart game above in the interactive diagram illustrates the difference between accuracy and precision. In this game, the accuracy is how close the worst throw is from the bull's-eye. This measures the accuracy of your technique.

The precision is the radius of the circle enclosing all the shots, or how consistently you shot all three darts.

Subject Index for all interactive diagrams - Pysics - Precision and Accuracy - Dart Game

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