Results 1 to 13 of 13

Math Help - How to get this number?

  1. #1
    Junior Member
    Joined
    Oct 2010
    Posts
    28

    Unhappy How to get this number?

    Very stupid question, but really need
    \Sigma x=24095,7 ( \Sigmax =n*m=25*963,828=24095,7
    \Sigma x^2=24991420,5
    how to get \Sigma x^2 ???
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member
    Joined
    Dec 2010
    Posts
    470
    I am having some trouble understanding your notation.

    Is \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.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Oct 2010
    Posts
    28
    it is formula \Sigmax=n*m
    n=25
    m= 963,828
    when we put numers we get
    \Sigma x=25*963,828
    Also is formula
    \Sigma x^2
    And i know just answer it's 24991420,5
    So what's formula to get this number ?
    If more concret what is \Sigma x^2???
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Senior Member
    Joined
    Dec 2010
    Posts
    470
    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?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Oct 2010
    Posts
    28
    how they get
    \Sigma X^2=24991420,5
    If we know that
    \Sigma x=25*963,828=24095,7
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Senior Member
    Joined
    Dec 2010
    Posts
    470
    This is the solution, not the original problem.

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

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

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

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

    Then
    \Sigma x_i = 1 + 5 + 7 + 8 and
    \Sigma x_i^2 = 1^2 + 5^2 + 7^2 + 8^2.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Junior Member
    Joined
    Oct 2010
    Posts
    28
    i ask how they get this number 24991420,5?????????????????
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Junior Member
    Joined
    Oct 2010
    Posts
    28
    hot get this X^2(0,95,24)=13,84 ???
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Senior Member
    Joined
    Dec 2010
    Posts
    470
    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 \Sigma x_i^2.

    Please tell me what the 25 data points are from the original problem.
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Junior Member
    Joined
    Oct 2010
    Posts
    28

    Follow Math Help Forum on Facebook and Google+

  11. #11
    Senior Member
    Joined
    Dec 2010
    Posts
    470
    Using the data given:

    \Sigma x_i = 1000.3 + 999.8 + 998.2 + 1001.3 + 1001.0 + 1000.1 + \ldots
    and
    \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?
    Follow Math Help Forum on Facebook and Google+

  12. #12
    Junior Member
    Joined
    Oct 2010
    Posts
    28
    Yes, I have done it...
    But now I have problems with
    X^2(0,95,24)=13,84 ???
    how they get 13,84?
    Follow Math Help Forum on Facebook and Google+

  13. #13
    Senior Member
    Joined
    Dec 2010
    Posts
    470
    Normally the X^2 values are looked up on a table.

    Since your original problem was answered, please start a new thread.
    Someone with better knowledge of statistics would be better at explaining this (post under statistics with the title "chi-squared rejection region").

    Remember to provide all the information about the problem in the new post.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: January 16th 2012, 01:21 AM
  2. Replies: 4
    Last Post: April 28th 2011, 06:20 AM
  3. Replies: 2
    Last Post: August 19th 2010, 09:32 PM
  4. Replies: 2
    Last Post: December 18th 2008, 05:28 PM
  5. Replies: 5
    Last Post: October 7th 2008, 12:55 PM

Search Tags


/mathhelpforum @mathhelpforum