Results 1 to 4 of 4

Math Help - mean and standard deviation

  1. #1
    Newbie
    Joined
    Apr 2009
    Posts
    2

    Question mean and standard deviation

    A new young executive is perplexed at the number of interruptions that occur due to employee relations. She has decided to track the number of interruptions that occur during each hour of her day. Over the last month, she has determined that between 0 and 3 interruptions occur during any given hour of her day. The data is shown below. (10 points)

    Number of Interruptions in 1 hour Probability
    0 interruption .40
    1 interruptions .30
    2 interruptions .20
    3 interruptions .10

    (a) On average, how many interruptions per hour should she expect?
    (b) What is the standard deviation of numbers of interruptions per hour?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by dvsdars@gmail.com View Post
    A new young executive is perplexed at the number of interruptions that occur due to employee relations. She has decided to track the number of interruptions that occur during each hour of her day. Over the last month, she has determined that between 0 and 3 interruptions occur during any given hour of her day. The data is shown below. (10 points)

    Number of Interruptions in 1 hour Probability
    0 interruption .40
    1 interruptions .30
    2 interruptions .20
    3 interruptions .10

    (a) On average, how many interruptions per hour should she expect?
    (b) What is the standard deviation of numbers of interruptions per hour?
    What formula have you been taught for calculating expected value?

    What formula have you been taught for calculating variance? Standard deviation?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Apr 2009
    Posts
    2
    I don't know the formula. I took stats a couple years ago and a friend asked me to help him out. That's the only question I couldn't answer. He didn't give me any formulas for solving it.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by dvsdars@gmail.com View Post
    I don't know the formula. I took stats a couple years ago and a friend asked me to help him out. That's the only question I couldn't answer. He didn't give me any formulas for solving it.
    Then what has your friend been taught? I doubt your friend would be asked to do these calculations if he had not been taught the formulae.

    Read this: Discrete Random Variables: Mean or Expected Value and Standard Deviation

    Standard deviation is square root of variance. And variance is E(X^2) - [E(X)]^2. And E(X^2) is calculated in the same way as E(X).
    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: September 8th 2010, 04:05 AM
  2. Replies: 5
    Last Post: May 18th 2009, 05:14 AM
  3. standard deviation and mean deviation
    Posted in the Statistics Forum
    Replies: 1
    Last Post: March 16th 2008, 06:09 AM
  4. i need standard deviation help
    Posted in the Statistics Forum
    Replies: 2
    Last Post: February 22nd 2008, 06:03 PM
  5. The mean and standard deviation
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: February 17th 2008, 09:15 PM

Search Tags


/mathhelpforum @mathhelpforum