
Title:
SD Social Networkers  Intro to Descriptive Statistics

Description:

>> I'm going to show you the answer to this, by doing it in a spreadsheet. You

could do all of these calculations, without any technology. And if you did that,

that's really great. It's always really good practice to calculate things

without using any technology, but just for the purposes of figuring out the

standard deviation, technology can really speed along this process. So I'm not

going to use any shortcuts here. We're going to do it exactly as we would if we

didn't have technology. So first we need to take the avearage of all of these,

we're going to sum them up. So we're taking the sume of all of these. I could

also just write equals a1 plus a2 plus a3 all the way to a10. And we'd get the

same thing. But why would we do that if we can simply write this. Now to take

the average all we do is divide by the number of values which is 10. So that's

just going to be 51,511.1. Alternatively, the nice thing about technology is we

can just do this. Take the sum, and divide by the total number. Do it all in 1

step. So now we have the average. Now we're going to subtract the average from

each 1 of these values. Not the opposite, where we subtract each of these values

from the mean. That's an important distinction. In this case, it doesn't matter

as much but in other statistical concepts that's an important distinction to

make. So we'll write equals A1 minus. The mean. So I'm subtracting the mean from

each of these values. Now I could just do the same thing here and write equals

a2 minus the mean but that would be tedious. We can just drag this down. When

you do that, remember that there has to be a little plus sign there. That means

you're successfully dragging it down. If you went like this, it won't do

anything. It'll just highlight the boxes. So here, we have the deviations from

the mean. Here, in the next column We're going to square each deviation. Equals

b1 squared. And again, we're going to drag it down. So we have the squared

deviations for each of these values. Now remember that the variance is the

average squared deviation. So we could just write. Average of c1 to c10. But I

want to make sure we go through all the other steps in between. So let's again

practice calculating the average just for clarity's sake. So the variants then

would be the sum of c1 to c10. Remember that's how you start out taking the

average, and then divide by 10. So here's the variance, and then the standard

deviation is simply the square root of the variance. So we'll write equals SQRT.

That's the shortcut for square root. And then we can just say C13. So we know

that the standard deviation is 6557.16 approximately. Now I want to point out

something really important before we finish this solution video. Here I simply

said equals square root of this cell C13. Whereas here, I wrote out the

whole average. The reason for that is because say I had but this all here, A13.

Then, when we drag it down, we don't get the right deviations. And we can double

click on it, and see what it did. Here, it took A4 minus A16, whereas here it

took A1 minus A13, which is what we wanted. But we want it to always stay A13,

which is why we have to make sure this is a constant. And the way to make sure

it's a constant is by just writing it. Notice also that all of these values

changed when these values changed because all these values are dependent of

these values So when we change it back we should again get the correct standard

deviation.