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Title:
SD Social Networkers - Intro to Descriptive Statistics
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Description:
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>> I'm going to show you the answer to this, by doing it in a spreadsheet. You
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could do all of these calculations, without any technology. And if you did that,
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that's really great. It's always really good practice to calculate things
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without using any technology, but just for the purposes of figuring out the
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standard deviation, technology can really speed along this process. So I'm not
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going to use any shortcuts here. We're going to do it exactly as we would if we
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didn't have technology. So first we need to take the avearage of all of these,
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we're going to sum them up. So we're taking the sume of all of these. I could
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also just write equals a1 plus a2 plus a3 all the way to a10. And we'd get the
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same thing. But why would we do that if we can simply write this. Now to take
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the average all we do is divide by the number of values which is 10. So that's
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just going to be 51,511.1. Alternatively, the nice thing about technology is we
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can just do this. Take the sum, and divide by the total number. Do it all in 1
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step. So now we have the average. Now we're going to subtract the average from
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each 1 of these values. Not the opposite, where we subtract each of these values
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from the mean. That's an important distinction. In this case, it doesn't matter
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as much but in other statistical concepts that's an important distinction to
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make. So we'll write equals A1 minus. The mean. So I'm subtracting the mean from
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each of these values. Now I could just do the same thing here and write equals
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a2 minus the mean but that would be tedious. We can just drag this down. When
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you do that, remember that there has to be a little plus sign there. That means
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you're successfully dragging it down. If you went like this, it won't do
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anything. It'll just highlight the boxes. So here, we have the deviations from
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the mean. Here, in the next column We're going to square each deviation. Equals
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b1 squared. And again, we're going to drag it down. So we have the squared
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deviations for each of these values. Now remember that the variance is the
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average squared deviation. So we could just write. Average of c1 to c10. But I
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want to make sure we go through all the other steps in between. So let's again
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practice calculating the average just for clarity's sake. So the variants then
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would be the sum of c1 to c10. Remember that's how you start out taking the
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average, and then divide by 10. So here's the variance, and then the standard
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deviation is simply the square root of the variance. So we'll write equals SQRT.
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That's the shortcut for square root. And then we can just see C13. So we know
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that the standard deviation is 6557.16 approximately. Now I want to point out
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something really important before we finish this solution video. Here I simply
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said equals square root of this cell C13. Whereas here, I wrote out the
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whole average. The reason for that is because say I had but this all here, A13.
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Then, when we drag it down, we don't get the right deviations. And we can double
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click on it, and see what it did. Here, it took A4 minus A16, whereas here it
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took A1 minus A13, which is what we wanted. But we want it to always stay A13,
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which is why we have to make sure this is a constant. And the way to make sure
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it's a constant is by just writing it. Notice also that all of these values
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changed when these values changed because all these values are dependent of
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these values So when we change it back we should again get the correct standard
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deviation.
