 often you're struggling a bit with the definitions of what is precise and what is accurate. So in this video I'm going to try to illustrate you an example what's the difference between being precise and being accurate. So the example I'm using is I'm going to measure the height of this person here. We have a little of curly hair here so we do have uncertainties in this measurement. Now there are four different answers that came up by somebody that measured one was well it is 180 centimeters plus minus 20 centimeters. Now this measurement here is accurate as with the plus minus 20 centimeters I'm very sure that the real value is actually in there but it's not very precise like plus minus 20 that means it could be anything from 160 to 200 centimeters. The first goal of any measurement is always to be accurate. Now the second measurement here reported 180 centimeters plus minus 2 centimeters. If I look here I'm confident that the real height of that little person here is within my uncertainty given. So in this case my measurement is accurate and precise. Accurate because my real value is probably in there and precise because I have a very low uncertainty. So high precision means low uncertainty while low precision means high uncertainty. Accuracy by itself means is the real value in there. So of course the goal of any measurement is to be accurate and precise but often this is difficult to achieve so we're going to settle first for being accurate and then we think of okay how can we improve our measurement methods so we can improve on that precision. Now there are two other possible outcomes. One is this one here when I'm not accurate but very precise. So again I'm giving an uncertainty a very low uncertainty but the value on which I apply this uncertainty is way off the real value so 170 plus minus 1 centimeter. So no way that the height of this person is 170 plus minus 1 centimeter. So in this case I had high precision but was not accurate. So measurement with high precision and no accuracy is kind of useless as with the real value is not in there. This happens often if you have a very precise instrument but there's something wrong with your measurement method or the instrument is offset. Often you can kind of adjust this one if you know why you're being off. And there is the last possible outcome where you're not accurate and not precise. For example here the person reported a height of 150 centimeters plus minus 20 centimeters so I'm way off the real height and on top I have a very low precision. So here this case is kind of the worst case scenario because there's not much I can do. Here I can probably fix it if I realize that there was a problem. The trick here is to realize that you have a problem because if you use a very precise instrument you might be inclined to believe that the instrument also gives you accurate results. That's not necessarily the case. They could be an offset, they could be other issues. They could be an issue with the object you're measuring, they could be an issue with the measurement method, they could be an issue with the person measuring. But if you know and analyze what's happening you could fix this. First goal is being accurate and ideally we get here where we are accurate and precise.