 In the last video I was measuring the length of a cat and then estimated the uncertainty of a measurement. I came to an answer that the cat has a length of 0.5 meters plus minus 0.4. Now estimating is good if you wanted to think about where your sources of the uncertainty are but definitely might not be the most comfortable thing to do because after all it is an estimation. So is there another way of figuring out the uncertainty? Yes there is. We can use statistics and in these statistics we have three different methods of doing it. We have the min-max method, we can use average deviation and we can use standard variation. In order to use statistics however you need much more than just one measurement so the downside of doing statistics is you need many measurements. So let's go do that. 35, 65, 51, 57. So I've measured the cat total of 18 times and I got 18 different values. So we're going to start with the min-max method. So what we need in the min-max as the name suggests we need to figure out what is the maximum value and what is the minimum value of all the measurements. I'm going to go through my numbers here. I'm looking for my minimum which is 0.41 meters and I'm going to look for my maximum. My maximum is 0.77 so max 0.77 meters and now how do we calculate the formula says we're going to calculate the value itself as simply the average of the min plus the max divided by 2 and then the uncertainty we take the difference so max minus min and we divide it by 2. If you think about it, if you have like several values what we do is we say okay this is the minimum value, this is the maximum value, our value we report is this with the uncertainty of exactly half the range between the minimum and the maximum. So our answer will include every single number here inside. So let's calculate gives me 0.59 plus minus now max minus min 0.77 minus 0.41 divided by 2 gives me 0.18 meters. So again we're talking here about many uncertainty many a lot of uncertainty so what I prefer to do is I'm going to round this to one significant figure so plus minus 0.2 meters and then I'm going to round this as so only I have only one estimated figure so 0.6 plus minus 0.2 is what I'm going to report using the min max method. So I can put my answer here next to it with the min max method I got 0.6 plus minus 0.2 meters. In the next video I'm going to show you how to use average and standard deviation to calculate it.