Results 1 to 3 of 3

Math Help - finding variance?

  1. #1
    Newbie
    Joined
    Dec 2009
    Posts
    8

    finding variance?

    heres the probability distribution table, it shows the number of tvs, n, sold per week:

    N 1 2 3 4
    P(N=n) 0.1 0.2 0.4 0.3

    with the information, the fixed costs of the business which sells the tvs is $900 per week and the profit per tv is $375, find the variance in profit each week!
    Last edited by sillylilly; February 17th 2010 at 09:54 PM.
    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 sillylilly View Post
    heres the probability distribution table, it shows the number of tvs, n, sold per week:

    N 1 2 3 4
    P(N=n) 0.1 0.2 0.4 0.3

    with the information, the fixed costs of the business which sells the tvs is $900 per week and the profit per tv is $375, find the variance in profit each week!
    Option 1: Construct a table for profit P and the associated probability. Note that P = 375N - 900. Then calculate variance from this table in the usual way.

    Option 2: Calculate Var(N) from the given table and then calculate Var(P) = Var(375N - 900) = 375^2 Var(N).
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Dec 2009
    Posts
    8

    thanks, but.....

    thankyou for your reply,

    I tried both these ways and the outcome in both cases was 125,156.25

    On one hand, because both ways got the same answer I would expect it to be correct, however that just seems far too great a sum to be true! Do you know what it is , if I am doing this wrong? Or is this the real answer!?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Finding the Variance of (1/S)
    Posted in the Advanced Statistics Forum
    Replies: 4
    Last Post: November 6th 2011, 08:56 AM
  2. Finding Mean/Variance from Sum of fi
    Posted in the Statistics Forum
    Replies: 1
    Last Post: March 10th 2011, 09:08 PM
  3. Finding mean and variance of RV
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: April 22nd 2010, 12:22 AM
  4. finding variance
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: April 17th 2009, 11:58 PM
  5. Finding mean and variance from the mean?
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: November 18th 2008, 02:56 AM

Search Tags


/mathhelpforum @mathhelpforum