Precision is about how tightly clustered your measurements are. Accuracy is about how well those measurements reflect reality. If you are just trying to see h

Precision is about how tightly clustered your measurements are. Accuracy is about how well those measurements reflect reality. If you are just trying to see how smooth a ball is by measuring the diameter many times at different points, then a high precision can tell you that, even if the actual diameter is different to your measurement. You don't care about the actual diameter, you care about the variation in it.