What is the difference between accuracy and precision?

When we make measurements while doing an experiment, the values we measure always have an uncertainty. We assign an uncertainty based on the equipment we are using and the way we make the measurements. If one measurement has a lower uncertainty than another, it is said to be more precise, i.e. have higher precision. It is the same when we use these measurements to calculate a final result for our experiment. If the calculated uncertainty is low, it is said to be of high precision.

 

When we compare our result to the accepted or actual value, the closer our result is to that value, the higher the accuracy. This means that the precision depends only on the uncertainty, while the accuracy depends on a comparison between our result and the actual value. A high-precision result can sometimes not be very accurate, and a low precision result can sometimes be very accurate. If the former scenario occurs, it is possible that we should rethink our estimates of the uncertainty for our measurements.