Accuracy and precision have very similar definitions—both describe the quality of results in a laboratory experiment. The difference between the definitions, however, is very important. Accuracy describes how close values are to widely accepted or published values. For example, if you measured the acceleration due to gravity, did you get 9.8 m/s2? Precision describes the quality of your measurements themselves. For example, how sure are you of them, and if you measure again, will you get the same result?
Look at the dartboard example below. Read the background information first. Remember, precision is how close all your darts are together. Accuracy is how close it hits the bull's eye.
Click the green circle to pick up a dart and quickly drag toward the dartboard. Your goal for the activity should be to get the accuracy and precision numbers as close to zero as possible. (If all three darts end up at the same place, the precision will be +/-0, and if that place is the bull's eye, then the accuracy will also be +/-0.)
Arch the arrow to better your chances of hitting the board. Make sure to practice.