Hello, and welcome to a video on summation in Excel. Summation is when simply
put, we want to find the sum of something. So either a sum after a set of calculations or the
sum of a data point, meaning a set of numbers, that sort of thing.
So let's say we have a problem that's asking us to find the sum of x. Well,
here's x right here. We can see that it's this collection of data. To find the sum in Excel,
we type equals sum, open parentheses, select
the variable that we'd like to find the sum for, close parentheses and hit enter.
And we can see that the sum of x is 44. And if you calculate this by hand, you can see that
that's the case. We can also find x bar
in Excel. x bar is the average of a sample. So in Excel, we'll
type equals average, open parentheses,
select the variable we'd like to find the average of, close parentheses and hit enter.
And you can see now, we have the average or x bar. We can do other
types of calculations in Excel as well. If we wanted to multiply x times y, we could do that
by saying equals x, asterisk, then selecting
y, and hitting the enter key. To repeat this
down the line, we'll just drag it from the corner here.
If I then wanted to find the sum of these numbers, I would type equals sum,
select the numbers, and close parentheses. The same is before.
Let's try x minus y. So open an equation by using the equals
sign, then select a2 minus b2 and hit enter.
And that's it. That's all you have to do to find the difference between two variables. Now, if we want to know
deviation or deviants, what we're looking for is x minus x bar.
So we would say equals x minus and x bar down here is this
number. To make it stay on that number, to make this number a constant. We're going
to use the dollar sign in front of a and the dollar sign in front of 13. This tells Excel when I drag this
formula down, don't move this box.
Okay, now we're going to drag that down. Let's
find the sum of our deviants. Here
we go.
As expected, the sum of our deviants is zero. This will always be the case.
What if we want to define the square of x minus x bar? There are a couple of ways
we could do that. We could say equals e to times e to
just like before when we found x times y except for multiplying it by itself. And that will get
us 4.714 squared and we could drag that down.
We could also use
the power function equals power,
select the number, and then select the power. Which in this case is
2 because we'd like to square it. It enter and then you would drag it down.
There is another way that you can find a square in Excel. And that's
by using the carrots symbol. So equals x minus x bar
raised to the power of 2. And we're using 2 again because we want to
square it. If we wanted to cube it, then we would use 3. If we wanted to raise it to the fourth or fifth power, then we would
use 4 or 5. Okay, so now that we've got x minus x bar squared, what if we wanted to find
the sum of x minus x bar squared? Well, of course, we would calculate that the same way we did before using
the equal sum function. And that's it. That's the sum of x
minus x bar squared.