Transcript:

Hello, and welcome to my secret math tutor this video. I want to show you how to make a scatter plot. So these are really great types of plots that we can use to help see relationships in our data to be a little bit more specific in a scatter plot. We use these to show a relationship between two variables now, usually a symbol, usually a dot is used to show an individual pair of data. Let’s look at some other terms that are also used when describing these scatter plots. We’ll take the data and take both of our variables and represent them along both of these axes here on the bottom one. We call this our x-axis. This is where we’ll display our independent variable along the other line. Our y-axi’s we’ll display the second variable. We’ll call this our dependent variable. Now you might be curious like how on earth do we know which one’s the dependent variable? How do we know which one is the independent variable? We’ll think of it this way. The dependent variable will change as a result of what the independent variable is doing. And when we get to my example, you’ll probably be able to more clearly see which one is depending on the other one’s value. All right, let’s give it a try. So we want to create a scatterplot for the following data and this chart or table here just represents the hours of studying and a particular exam score that some students had so which one of these would depend on the other one well. We would think that whatever exams square they got probably depended on the hours of studying, so we will say that the hours of study are independent and the exam scores are dependent there. We go now. It’s also important to mark out a scale so we can put all of these data values in here and looking at the hours of study. It looks like somewhere between zero and ten hours is probably good, so lets mark off. Ten’ll tick marks so zero One, two, three, four, five, six, seven, eight, nine, ten one, two three, four, five, six, seven, eight nine. Oops, got an extra one. Ten, all right along the other side. This is where our exam scores will go. Let’s just do zero to 100 so 10 20 30 40 50 60 70 80 90 100 Okay, looks good now. The way this works is, we want to put a data point at the intersection of hours and scores so that that one point represents a pair of data. Let’s start off with the first one, so we want to put two two hours of studying and a score of 53 so we’ll first find the hours of studying. There’s our two and we’ll put a dot where it intersects 53 so just a little bit above the value of 53 Okay, not that, let’s do this again, So we got four and a half for 35 so four and a half halfway between up to ten twenty thirty and a half, not bad, Okay, up to five five needs. Go all the way up to 91 so way up here. Let’s keep going. We also have five, which is at 72 Let’s see so 50 60 70 – notice how we get two values of both four five and that’s okay. Sometimes that can happen with these scattered. Let’s see six. We need a dot at 63 We need one at 62 lets. See ten over here. We need one. At 85 50 60 70 80 halfway 85 Let’s see nine and a half so halfway between these two, This one’s going up to 78 so 50 60 70 almost 80 But not quite. Let’s see one more eight. Ah, there almost got a perfect score 99 way near here, the top, so the advantage of having something like a scatter plot to see all of your data points is you can start to see if there’s possibly relationships among these two different variables. And you know if I was looking at this, and if it was, you know, real data, you know, I might expect that maybe exam scores Are, you know, really have a strong relationship with the hours of studying? Maybe the more we study the higher. Our scores are now. If this is our data, then you know, actually looking at maybe. I’m not convinced that these two things are really related because you know the people who are studying. A lot aren’t really scoring a whole lot better than some people who only score a little bit. They’re still actually scoring pretty good, but it’s a nice visual way that we can see those relationships and get a sense of what is happening between those two variables. All right, we’d like to see some more videos. Please visit mysecretmathtutorcom.