Page 1 of 2 12 LastLast
Results 1 to 10 of 13

Thread: Need help with the Mean formula

  1. #1

    Need help with the Mean formula

    I thought I understood the formula, but I can't figure out how to set it up for this problem. compute.jpg

  2. #2
    Elite Member stapel's Avatar
    Join Date
    Feb 2004
    Posts
    15,851

    Cool

    Quote Originally Posted by Inferno View Post
    I thought I understood the formula, but I can't figure out how to set it up for this problem.
    Which formula? What did you plug in, where? Where did you get stuck?

  3. #3
    this formula http://sph.bu.edu/otlt/MPH-Modules/B...eanFormula.png

    . . . . .[tex]\bar{x} \, =\, \dfrac{\Sigma X}{n}[/tex]
    Last edited by stapel; 09-12-2013 at 11:41 AM. Reason: Providing formula inside post.

  4. #4
    Elite Member
    Join Date
    Jun 2007
    Posts
    17,571
    Quote Originally Posted by Inferno View Post
    So now tell us what did you plug in? what did you get?
    “... mathematics is only the art of saying the same thing in different words” - B. Russell

  5. #5
    I am pretty sure I plugged the stuff in wrong. here's what I did for Set A

    E20/6 = 5x10
    E3.3 = 50
    E=15.1

    and set B

    E20/6 = 50x10
    E3.3=500
    E=151.5

  6. #6
    Elite Member
    Join Date
    Jun 2007
    Posts
    17,571
    Quote Originally Posted by Inferno View Post
    I am pretty sure I plugged the stuff in wrong. here's what I did for Set A

    E20/6 = 5x10
    E3.3 = 50
    E=15.1

    and set B

    E20/6 = 50x10
    E3.3=500
    E=151.5
    Okay that is not the way to work with mean (or average).

    Tell us the definition of mean (or average).
    “... mathematics is only the art of saying the same thing in different words” - B. Russell

  7. #7
    mean is when you add all the numbers up and divide by how many there are

  8. #8
    10+20/6 = Set A is 5?

    and 500+20/6= Set B is 86.7 ? are those right? I did that without the formula because the formula confuses me.

  9. #9
    Elite Member
    Join Date
    Sep 2012
    Posts
    2,728
    Quote Originally Posted by Inferno View Post
    10+20/6 = Set A is 5?

    and 500+20/6= Set B is 86.7 ? are those right? I did that without the formula because the formula confuses me.
    The formula is not confusing. The problem is confusingly worded because it changes the definitions of the sets.

    For set [tex]A = \{x_1,\ x_2,\ x_3,\ x_4,\ x_5\}.[/tex]

    [tex]\displaystyle \bar x_A = \dfrac{\displaystyle \sum_{i=1}^5x_i}{5} = 10 \implies\sum_{i=1}^5x_i = 5 * 10 = 50.[/tex] Follow that?

    Now let's define a new set [tex]H = \{x_1,\ x_2,\ x_3,\ x_4,\ x_5\, x_6\},\ where\ x_6 = 20.[/tex]

    So [tex]\displaystyle \bar x_H = \dfrac{\displaystyle \sum_{i=1}^6x_i}{6}.[/tex] Still using the formula.

    But what is the numerator in that formula equal to?

    Here is the trick

    [tex]\displaystyle \sum_{i=1}^6x_i = \left(\sum_{i=1}^5x_i\right) + x_6.[/tex] Does that make sense?

    And we know what the two terms on the right of the equation equal.

    [tex]\displaystyle \sum_{i=1}^6x_i = 50 + 20 = 70 \implies \bar x_H = \dfrac{70}{6} \approx 11.67[/tex]

    Now try the second problem on your own, and let us know what you get.

  10. #10
    50x10= 500

    500+20= 520

    520/6 = 86.7

    still wrong? lol

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •