Accuracy and precision both have different meanings. When we talk about accuracy, we refer it to how closely the data is with the true value, while precision is how close single measurements are together. It’s easy to visualize, imagine you’re shooting at a target; your goal is to aim at the “bulls-eye” or expected target. Being accurate is your ability to get your shots close to the center; when precision is having your targets group together in a close bunch, though they may not be near the bulls-eye. These ideas are important when we talk about numbers, more importantly, significant numbers. Significant numbers are a degree of accuracy, having exact and inexact numbers. Numbers that are know and certain are exact, while inexact are those who are unknown, for example, if I say a car is $9,000, then that number can be anywhere between under 10,000 and more than 8,000. Only 1 significant number was in 9,000; but if I use a more accurate number like $9,239 then it’s an more accurate than just 9,000 because more numbers are know and a greater amount of significant numbers. Even the atomic weight was changed because we found more accurate numbers that changed the weight of 19 elements.