>> In this video I'll be explaining the mean.
So let's find the mean on this data set.
To do that we add all the values and then we divide
by how many values we have.
And so a mean is nine or another way
of saying it is the average is nine.
Another way to explain the average,
instead of using a formula, is by saying
that the average is a balance, so let me explain.
Remember when you used to play the teeter totter?
Well the board and this thing called the fulcrum
or a balance point.
And you and your friend would have to find a position
so that you can both be balanced.
Well, same thing with an average.
So you do a dot plot for example on your data set
and you know your average is nine.
Well that's going to be your balance point,
your fulcrum, let me explain.
Let's draw a vertical line at nine, which is your average
and let's figure out the distance
between the mean and each point.
So, one point to the right of nine is eleven.
The distance there is two.
And you'll notice that on the left
of nine there's also a data point at seven.
We can say that distance is negative two.
You can think of it as a distance
to the left of the mean.
You just think of distance can also be negative in this case.
So negative two and two, they balance out.
And then nine to 13, that's a distance of four.
Is there something to counter balance that?
Yes, on the other side of nine from the left of nine,
go all the way to five, that's going to give you negative four.
So again there's a balance.
Believe it or not every single data set turns
out to be this way.
Another way of explaining the average is
that every single value of your data set can be turned
into a nine.
So every value in the data set could be turned
into the average.
How's that?
Well here each value of my data set is in different color
and you can see like the orange is nine and the green is 11,
the yellow is 13 and the blue is seven and the purple is five.
Now I can turn the 11 column, the green one, into a nine.
How do I do that?
Well I just take away two green squares
and if I take those two green squares and put them next
to the blue, you'll see that those numbers now become nine.
The green was 11 and it turned into nine when I took away two
of those green squares.
And I put them into the on top of the blue
and the blue was seven, right.
And I put those two green squares
and now they become nine.
How about the yellow?
If I want to make it nine because right now it's 13,
let's take away four of those yellow squares and put them
in the purple column and there you go.
Thirteen became nine and five, which was the purple,
I added those four yellow ones, it also became nine.
So, all the numbers became the average.
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