 Next, we're going to go through the scientific usage of the words accurate and precise. In everyday language, these are used to mean the same thing, but scientists make a careful distinction between the two. The statement that Australia is in the southern hemisphere is accurate, but not very precise. But if I say Australia is centred on the South Pole, then I'm being very precise, but not at all accurate. As we've just discussed, when you repeat a measurement many times and use different equipment or methods, you'll probably get some variation in the values due to random and systematic errors. Now if there's a small spread of values, with a small amount of measurement uncertainty, we're going to call these measurements precise. If we take the average of all the measurements and find that it's close to the true value, then we say the result is accurate. Now precision and accuracy are not the same thing. It's possible to have experiments that are very precise but not accurate, and others that have low precision, but where the average of many measurements is spot on the true value. Now you might notice that accuracy and precision are closely related to the presence of systematic and random errors. An experimental setup that has significant systematic error won't give accurate results. And similarly, large variations in measurements due to random error will mean the results are not precise.