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Homework Help: Find mean and variance of X and Y

  1. Sep 11, 2010 #1
    1. The problem statement, all variables and given/known data

    I have found the marginal distribution for X and Y from a table. (No statistical regression, just simple table)
    How should I proceed in finding mean, variance an correlation coefficient of X and y? I am computing by hand.
    Thank you,



    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Sep 11, 2010 #2
    Is mean for X:

    (1/8+3/8+3/8+1/8)
    -------------------
    4

    and mean for Y is

    (2/8+4/8+2/8)
    --------------
    3

    ?
     
  4. Sep 11, 2010 #3

    vela

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    No. Remember the mean of a random variable is defined as

    [tex]\bar{X} = \sum_i x_i P_X(x_i)[/tex]

    It's the sum of the product of the values X can take on multiplied by probability of that value.
     
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