In this video I'm gonna try to measure the length of a cut. This cut. As you can imagine there will be a couple of difficulties doing so. About 41 and 62 with the Q. So after several attempts of measure they can't, I finally got a value. I got 41 without the Q and 62 with the Q. Sorry there is quite some discrepancy. Now the question is what is the uncertainty of that measurement? So one way of getting the uncertainty is like estimating it. It's probably the fastest way because you only need to take one measurement to estimate it. But it will probably produce one of the lowest precision if you do it right. So let's look how we do. First, what could my own very positive uncertainty come from? Well one factor is the tool I was using. This is the one every one of you is familiar from Echo, from Chemistry. You take the lowest, how is the lowest increment of your tool? My case my meter stick had an increment of 1 millimeter. So an uncertainty of 0.005 meters. Next one is the object that I measured. Was it have a good size? Like my cap? Do I measure the whiskers? There is hair. Do I measure the hair or not? Do I measure the tail or not? So just for the tail I think I could have been easily off in this case by 20-17 years. Then next one, the method I'm using. I was trying to run after the cut with the meter stick. Probably not the most precise way to do it. Maybe I could have fact the cut or a drug or try to measure her in the sleep. So I think I could have been off through it from the method by good one 10 centimeters because maybe it was still a bit curved. And then finally the human error of me, how good did I do the chopper? Was I paying a lot of attention? Did I concentrate a lot? I was mostly concentrated just running after the cut. So I think I could have maybe been off by a good 5 centimeter here as well. So these are all estimations. So don't forget these estimations. Then what I'm doing I'm adding them up. So 5, 5, 3, 0. So I could have been off according to this estimation by good 35.5 centimeters. Now if I've already had this as an estimation, so let's not pretend the precision that we don't really have. So I'm going to run this to 0.4 meters of uncertainty. So what do I record as the final answer? Well, I'm going to take value in between. So 0.5 plus minus 0.4 meters. This will be the final answer for the length of my cap. 0.5 meters plus minus 0.4 uncertainty. Is that precise? No, absolutely not. This is not precise. Oh, I have an uncertainty that's almost the size of my value. What it actually means is you could be anything from 0.1 to 0.9 meters. So precision, very bad. However accuracy, accuracy meaning am I absolutely sure that the real value is in there? Yeah, I'm absolutely sure. My cap is definitely longer than 10 centimeters. It's definitely shorter than 9 to 10 meters. Actually, probably most cats in this world will fit into this. So a curiosity of this measure was good. Precision was low. So the next step would be to think how can we improve precision? Then we go back at our estimation table and we see where the most of the uncertainty come from. Most of the uncertainty came from that we didn't define if we main cat with the Q or without the Q, with the whiskers, without the whiskers. So we can improve this uncertainty a lot. Another big contributing factor was the method. So the method here, tensor, the minus was running after the cap. Maybe I should have given her some food, measure the cap when sleeping, that would have helped. And then you looked at the one that always are blamed, crappy equipment, and human error. In this case, there were almost not significant contributors to the uncertainty. The main uncertainty came from the object itself and the method of measurement. Not from the human measuring it. And absolutely not from the probably 50-year-old meadish state I was using.