Results 1 to 3 of 3

Math Help - variance problem

  1. #1
    Junior Member
    Joined
    Oct 2008
    Posts
    39

    variance problem

    Q:
    n people put their watch in the center of a room where the watches are mixed
    together. Each person then randomly selects one. Let X represent the number that select their own watch. Find the expected value and variance of X.

    I found the expedted value to be 1. ( sum to n 1/n*1). So variance i have
    sum 1/n(x_i - 1)^2 = 0

    is the variance correctly 0?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    it can't be zero.
    that means X is constant, wp1
    What is your probability distribution?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by CarmineCortez View Post
    Q:
    n people put their watch in the center of a room where the watches are mixed
    together. Each person then randomly selects one. Let X represent the number that select their own watch. Find the expected value and variance of X.

    I found the expedted value to be 1. ( sum to n 1/n*1). So variance i have
    sum 1/n(x_i - 1)^2 = 0

    is the variance correctly 0?
    What you need can be found here: Rencontres numbers - Wikipedia, the free encyclopedia
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Mean and Variance problem
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: July 20th 2010, 05:04 AM
  2. variance problem (i think)
    Posted in the Statistics Forum
    Replies: 10
    Last Post: January 21st 2010, 07:16 AM
  3. help with a sampling variance problem
    Posted in the Statistics Forum
    Replies: 1
    Last Post: December 3rd 2009, 06:54 PM
  4. Variance problem
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: July 19th 2008, 08:09 PM
  5. Variance Problem
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: April 7th 2008, 08:30 AM

Search Tags


/mathhelpforum @mathhelpforum