00:01
A standard deviation, and we're assuming it's a sample size.
00:04
There's a difference between sample and population.
00:09
So when we're looking for the sample size, the first thing we want to do is we want to find the mean of the data.
00:16
So you're going to add all the data together.
00:19
So in this case, we have 13 plus 24, plus 21, plus 26, plus 9, plus 21, plus 22, plus 15, plus 21, plus 16, and plus 16.
00:41
That's going to give you 204.
00:46
You're going to then divide it.
00:47
There's 11 pieces of data.
00:49
So you're going to do 204 divided by 11, and that's going to give you approximately 18 .5.
01:00
Okay? so that's your mean.
01:05
So now you take each one of the data points, subtract your mean from that, and then square it.
01:11
So for example, i would do 13 minus 18 .55 squared.
01:21
And i'm going to do that for each one of those.
01:25
So then plus the next one, 24 minus 18 .55 squared...