all right so uh we've talked a little about making graphs and charts and how to do the basics of that in excel or on google so i'm going to add kind of add another layer to that this week and we're going to talk about uh how to add error or a representation of standard deviation and so i've had you read a couple of articles on that and so now we're going to look at kind of how how to make that work and why that's important when it comes to data and so the reason for that is because you're probably going to have to do something like this on your final poster you're going to be collecting some assortment of data and your you may be kind of you averaging it out essentially and creating a single a single graphical representation but that needs to include some representation of the variation uh that's inherent in the system so what do i mean by that that sounded like a bunch of gobbledygook perhaps all right so let's take our example from uh our previous example so this is kind of the graph that i ended up with of pirate scene per year and this is this is really great and again this is where the the type of graph or chart has to match what it is you're trying to accomplish with your with your graph so this graph is really great if i'm trying to compare 2020 versus 2021 and i want to see like what's the difference in time with respect to these two kinds of things uh and so there are situations where that is necessary and appropriate and exactly what we're trying to do but there's also situations where i just want to know i collect a bunch of years worth of data and i say i want to know on average how many pirates i should expect to see in a given month right and so here you can kind of look at two years worth of dating yeah okay i guess probably get some sense of this just you know by looking at it what if you've got like 30 years worth of data right trying to draw 30 different colored lines here is gonna it's going to be messy it's going to look like a disaster and no one's going to want to look at that and so you need to be able to combine that data so i really want you to find some sort of some sort of whatever test you're running with your with your game for your final poster you need to be able to combine it and average it so that you can do this and demonstrate that you know how to do this so if we want to combine these two kinds of things uh the simplest way this is a really simple way of doing it is to take what's called the average or the mean so you'll see sometimes professors do this with test scores or something it's like what's kind of the middle or the average uh and so for example i've done this with only two but you could do this with a lot more so i s in 2020 we saw three pirates in january 2021 we saw two and so if we the average of that is two and a half so one way to calculate average is that you sum up the all the different things that you see in this case 3 and 2 and then divide by the number of times it occurs so 3 plus 2 is 5 divided by 2 occurrences of that is 2 and a half right so if i had 30 data points i would add up 30 different things and then i would divide by 30. so excel i'm not a i'm not an excel mastermind but uh there are a few tricks that you can do so for example uh it you can take the time and go through and just write out something like all right let's see equals this plus this divided by 2. now that's not going to be right and the reason that's not right is because it's doing order of operations so division comes before addition in this case so it's taking 2 divided by 2 which gives you 1 and then it's adding it to 3. so in that case we have to add in parentheses thusly and then that will give us the right answer so you can do that or and so or you can just do what i've done here which is you just type in equals average and then you put in the squares that you wanted to average for you so slight shortcut particularly if you've got a lot a lot of a lot of data points all right so i've got an average here and i have then graphed this average over here on the right um and so you can see uh basically a graph of the average so we would basically say looking at this all right we expect to see the most pirates in june july and august roughly speaking great however this gives us really no indication of how much variance there is in the values that we see so the average value here is well i'll pick this one because it's easy the average value here is uh is 10 in june right but that could easily be because in year one we had 10 and in year two we had 10 or it could be because in year 1 we had 20 and in year 2 we had 0. right so that 10 may not be telling us a whole lot so i'll show you what i mean so this this graph here is a graph um this first this first graph here that we looked at is a graph of the data from um uh that the first chart and i showed you some of that so this graph here is a graph of this data here so two two years worth of data all right great so far so good now if you look the graph directly below it looks like it's identical right these two graphs look totally identical however this graph here is actually a graph of this data and you'll notice maybe that the average values here average for january is the same as the average for january here the average for february is the same as the average there the averages the means for these two different sets of data are exactly the same so it looks like basically there's no difference at all and so this is why the standard deviation is going to is going to be really helpful and tell us what's going on and so uh the the articles that i sent you to talk a little about how to calculate those again excel has got some nice little shortcuts so instead of doing that nasty little formula for variance and square roots and all that other stuff you can just put in this this this thing here s t d e v dot p and then the data that you wanted to take a standard deviation of so in this case i've got these two values um here so it gives me a standard deviation of 0.5 and then once i've done that i can just do what's called fill down which basically means that it takes this formula here and then it uses that same formula uh and all of the the squares down here so i've got my standard deviations for this set of data in this column right here you can see that under the column it says standard deviation p and so i did the same thing with this other set of data here again remember the means look exactly the same and so i did calculate the standard deviation for each of these each of these values all the way down great all right so how how do we put the standard dv now we've calculated the standard deviations they're just numbers we need to actually do something with them right uh so how do we make that happen all right so again excel has got some some nice things i don't know that google can do this they're they're their capabilities are quite limited with respect to this so uh doing this in excel or finding someone who has excel would be really great but again if you click uh if you click on the the chart over here on the right you can't see it on your screen uh right now but there's like a little toolboard that comes up there's a little green plus sign there's a little paintbrush and then there's a little filtery thing i'm going to click the green plus sign and it gives me a list of chart elements and yeah we looked at this list a little bit when we talked about how to make a graph but this time i'm going to go down to this thing that says error bars and under error bars i'm going to click the little arrow here over here on the left it gives me options for standard error percentage standard deviation or more options i'm going to click more options okay and then i've got i've got a whole suite of things here that just showed up so let me see if i can move well let me move me there i go there's a whole suite of things that i can now do right i can put little caps on my error bars i can make it so that it only shows for example the plus side error bars i like doing both you can do cap or no cap and then there's all these different error amounts kinds of kinds of things down here so let's see here i'm going to go down here to custom can you see that yes you can see that i'm going to go to custom and then specify i've got both specify value right because i calculate it out and then you can't see it but a little box will pop up that says positive error value and negative error value and so i calculated all the standard deviations so i know what i want to put in here and so i'm going to just under positive error value i'm going to click the standard deviation from january and then i hold shift and click the last bit of data and then i'm going to do the same thing for the negative error value the same data and i just hit okay and then lo and behold i've got standard deviations in here great so let's see what that looks like there we go that's what that looks like so you can see the standard deviations there and so now what's going to be really interesting is let's compare the standard deviations for this data set versus the standard deviations on the other data sets so just give me a second here i will do the data here sorry i know you can't see everything that's happening i do apologize for that but i tried to describe it you can also again you probably can find tutorials on on how to do this so okay great that should do it there you go all right so now if we were to compare these two graphs you can see they're quite different right in terms of the amount of variation there's significantly more variation in this bottom graph than there is in the top graph so what looks to be the same and we're going to talk more about looks and how you can change and alter and do weird things with graphs to kind of dis trick or manipulate them so these two graphs initially look to be identical sets of data based just on the mean but now we see that's not entirely true because we have now been a bit more honest essentially and revealed the standard deviation so the amount of variance of these values um and so this might be let's say that this top graph is the number of pirates seen um on the west coast of europe uh in 2021 20 20 20 to 21 and this bottom graph may be the number of pirates seen on the east coast of china or i don't know whatever and so they made lucky like oh you see the same number of pirates but you now know like oh this gonna be in china there's a lot more variation so in any given year you might see a lot more or you might see a lot less in this given time than say compared to europe where it's it's a bit more constant it's a bit more predictable there's not as much variation and so doing something like this can be can be quite quite revealing when you learn to use standard deviation to that to that effect so again i don't um i don't know that google sheets has this capability to to manually custom modify your standard deviations but that's how you do it and i hope i expect to see some of that on on your final data for your posters so again take a look at this uh pause it rewind it go back if there are questions also you can feel free to email me if you're having trouble but i'd also recommend there's plenty of youtube stuff on this as well i think there may be there may even be help uh help function out yeah look at that help functionality within excel uh up there on the top the the top toolbar that you can search for things like custom custom error bars and stuff like that so quite a bit you can manage with that anyway that's how that works again there are uh sarah some of you who are probably excel experts uh would be my guess and there's a ton of shortcuts and some really cool things you can do at excel but for now um i'm just trying to give you some of the some of the kind of the more basic uh the more basic functionality particularly for us so but i'm looking forward to seeing some of your creativity at play when it comes to the posters but that's that all right thanks very much