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Dot Plots

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This tutorial covers dot plots.

Dot plots or graphical display for qualitative or for quantitative data. When you're creating a dot plot, you start by drawing an axis. An axis is those lines that kind of border off your graph. We can just draw a horizontal axis when doing a dot plot, or you can have a vertical axis as well.

When you're doing a dot plot, each observation-- each data point-- gets marked with a dot, and that gives the name "dot" to dot plot. And the relative heights of the dots show the distribution. So just roughly, each dot would represent an observation, and the heights of these lines of dots are going to give us some information about our relative distributions. Sorry, these heights are going to give us information about distributions. It's the relative heights that are telling us that.

So if we have our example here, we would want to start by making a consistent axis. So we're going to go 60, 65, 70, 75, 80, 85. And then we're going to get this out of the way. So 60, 65, 70, 75, 80, 85. And it doesn't matter how far apart you space it or what numbers you picked to mark the spacing with as long as you're consistent. So once I did 60, and then 75, I couldn't then put 75 right here.

Now, each of these numbers is going to get a dot. So 60 gets a dot, and 61-- I'm going to estimate-- 63, 65, 66, 67, 71. Now, 71 has 3 values, so they're going to stack on top of each other. Same with 73, it has 2 values. 74 has 2 values 75 has 3 values. 76 has 2 values. 79 has 2 values. 80 has a value. Sorry, 81 has 2 values. 82 has a value, and 83 has a value.

Now, the matter of where you place your dots, the size of the dots, and spacing between the debts, again, doesn't matter as long as it's consistent because now we're using the relative height to show our distribution. So you can see it stays pretty flat. There's more values here in the middle, and then it starts to lower down again at the end, but not as severely.

When you're making your dot plot, consistency is the key. And you could do this also with qualitative variables instead. So you could have a list down the bottom showing your favorite type of ice cream, and then put a dot for each value that has that type of ice cream. So this has been your tutorial on dot plots.