Results 1 to 2 of 2

Thread: standard deviation help please!!

  1. #1
    Apr 2009

    Unhappy standard deviation help please!!

    A small-business owner must hire seasonal workers as the need arises. The following list shows the number of employees hired monthly for a 5-month period.

    4, 13, 5, 6, 9

    If the mean of these data is approximately 7, what is the population standard deviation for these data?

    I have never done standard deviation in my class before-this question was from a sample of the CAHSEE. Please help and explain how I can do this problem.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member Twig's Avatar
    Mar 2008



    Do you know who to calculate the variance from sample?
    You take every value and subtract from it the mean, then you square this number, and do this for all data.
    that is,

    $\displaystyle \mbox{Variance } = s^{2} = \frac{1}{n-1} \sum_{i=1}^{n} \, (x_{i} - \mu^{*})^{2} $

    The standard deviation is the square root of the variance, so:

    $\displaystyle \mbox {Standard deviation } = s = \sqrt{\frac{1}{n-1} \sum_{i=1}^{n} \, (x_{i} - \mu^{*})^{2}} $

    The reason for dividing with (n-1) has to do with sample size, since n is small here, use (n-1), as written.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Standard Deviation
    Posted in the Statistics Forum
    Replies: 4
    Last Post: Sep 8th 2010, 03:05 AM
  2. Replies: 5
    Last Post: May 18th 2009, 04:14 AM
  3. standard deviation and mean deviation
    Posted in the Statistics Forum
    Replies: 1
    Last Post: Mar 16th 2008, 05:09 AM
  4. i need standard deviation help
    Posted in the Statistics Forum
    Replies: 2
    Last Post: Feb 22nd 2008, 05:03 PM
  5. The mean and standard deviation
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: Feb 17th 2008, 08:15 PM

Search Tags

/mathhelpforum @mathhelpforum