# Thread: How to get this number?

1. ## How to get this number?

Very stupid question, but really need
$\displaystyle \Sigma$$\displaystyle x=24095,7 (\displaystyle \Sigmax\displaystyle =n*m=25*963,828=24095,7 \displaystyle \Sigma$$\displaystyle x^2$=24991420,5
how to get $\displaystyle \Sigma$$\displaystyle x^2 ??? 2. I am having some trouble understanding your notation. Is \displaystyle \Sigma suppose to be a summation? Are there bounds for the summation? What is meant by 24095,7? Is this one number, two numbers, a pair? Please clarify. 3. it is formula \displaystyle \Sigmax=n*m n=25 m= 963,828 when we put numers we get \displaystyle \Sigma$$\displaystyle x$=25*963,828
Also is formula
$\displaystyle \Sigma$$\displaystyle x^2 And i know just answer it's 24991420,5 So what's formula to get this number ? If more concret what is \displaystyle \Sigma$$\displaystyle x^2$???

4. Ah, so 24095,7 means 24095.7 (= 24095 + 7/10) correct?

Where do you get the numbers n and m from?

From what I can tell, you have not given enough information to solve this problem.

What was the original statement of the problem?

5. how they get
$\displaystyle \Sigma$$\displaystyle X^2=24991420,5 If we know that \displaystyle \Sigma$$\displaystyle x=25*963,828=24095,7$

6. This is the solution, not the original problem.

In general, $\displaystyle \Sigma x_i^2$ cannot be determined by just $\displaystyle \Sigma x_i$.
I'm guessing that your problem provides data for $\displaystyle x_i$.

$\displaystyle \Sigma x_i$ means the sum of all $\displaystyle x_i$
$\displaystyle \Sigma x_i^2$ means the sum of all $\displaystyle x_i^2 = x_i \times x_i$

They are computed individually. If you read the solution again, it does not say it found $\displaystyle \Sigma x_i^2$ from $\displaystyle \Sigma x_i$.

Example: If I had data points 1, 5, 7, 8 for $\displaystyle x_i$

Then
$\displaystyle \Sigma x_i = 1 + 5 + 7 + 8$ and
$\displaystyle \Sigma x_i^2 = 1^2 + 5^2 + 7^2 + 8^2$.

7. i ask how they get this number 24991420,5?????????????????

8. hot get this X^2(0,95,24)=13,84 ???

9. Kristina
There really is not enough information from what you have told me.

You never actually showed me the problem, only a worked out solution to the problem. There is some information that the solution does not tell me.

From what I gather, the original problem gave you 25 data points. You have not told what the 25 data points are. Without this, it is not possible to know how they computed $\displaystyle \Sigma x_i^2$.

Please tell me what the 25 data points are from the original problem.

10. Using the data given:

$\displaystyle \Sigma x_i = 1000.3 + 999.8 + 998.2 + 1001.3 + 1001.0 + 1000.1 + \ldots$
and
$\displaystyle \Sigma x_i^2 = 1000.3^2 + 999.8^2 + 998.2^2 + 1001.3^2 + 1001.0^2 + 1000.1^2 + \ldots$

and these come out to be the answers provided. Make sense now?

11. Yes, I have done it...
But now I have problems with
X^2(0,95,24)=13,84 ???
how they get 13,84?

12. Normally the X^2 values are looked up on a table.