Results 1 to 2 of 2

Math Help - Explanation Please

  1. #1
    Member
    Joined
    Oct 2008
    Posts
    124

    Explanation Please

    Mark found the mean of 26, 32, 22, 35, 25 using the strategy below. Why is his strategy valid???

    "I guessed the mean was 30. Then I found the difference between each data point and 30 and I got -4, 2, -8, 5, -5. The average of these numbers is -2. So 30 and -2 is 28, which is the average of the original data set."
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Nov 2008
    From
    France
    Posts
    1,458
    Quote Originally Posted by bearej50 View Post
    Mark found the mean of 26, 32, 22, 35, 25 using the strategy below. Why is his strategy valid???

    "I guessed the mean was 30. Then I found the difference between each data point and 30 and I got -4, 2, -8, 5, -5. The average of these numbers is -2. So 30 and -2 is 28, which is the average of the original data set."
    Hi

    Let (x_i), i=1 \cdots n be the set of values
    Let \overline{x} = \frac1n\:\sum_{i=1}^{n}x_i be the average
    Let X be Mark's estimation

    Mark calculated the differences X - x_i, i=1 \cdots n
    then the average
    \frac1n\:\sum_{i=1}^{n}\left(X - x_i\right) = \frac1n\:\left(\sum_{i=1}^{n}X - \sum_{i=1}^{n}x_i\right) = X - \frac1n\:\sum_{i=1}^{n}x_i = X - \overline{x}

    Therefore \overline{x} = X - \frac1n\:\sum_{i=1}^{n}\left(X - x_i\right)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. ACF() Explanation
    Posted in the Statistics Forum
    Replies: 0
    Last Post: January 18th 2011, 10:24 PM
  2. I need an explanation
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: February 1st 2010, 09:09 PM
  3. i need explanation
    Posted in the Geometry Forum
    Replies: 1
    Last Post: July 9th 2008, 09:00 AM
  4. Help with an explanation
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: May 1st 2008, 03:00 AM
  5. Explanation
    Posted in the Number Theory Forum
    Replies: 2
    Last Post: February 7th 2006, 02:55 PM

Search Tags


/mathhelpforum @mathhelpforum