 Hi, I'm Vanessa at the Research School of Physics today and you and today I'm going to talk to you about Uncertainties and measurement now every time you make a measurement It has a finite amount of precision and each time you do an experiment It's always going to turn out a little bit different each time And so as scientists we not only need to quantify what we're measuring We also need to quantify the error or uncertainty in that measurement and that's what we'll go through now First let's clarify the scientific use of three words error uncertainty and mistake Error is the difference between what you measure and the true value of the quantity The uncertainty in a measurement is your best estimate of the range of values You think the true value will lie within and mistakes and when you perform a measurement incorrectly Scientific methods try to minimize the possibility of mistakes as much as possible We'll discuss each of these terms in more detail in the following material