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Math Help - Statistics

  1. #1
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    Statistics

    I had a test today. Heres one of my questions. Can someone do it, because im not sure if I got it right, and I'd like to know now.

    You have two different dice. One die has a 1 and five 3's.
    The next die has four 2's and two 6's.

    Like this:

    Die 1- 133333
    Die 2- 222266

    Set up this table:
    X __ __ __ __
    p(X) __ __ __ __

    What is the mean?
    What is the standard deviation?

    For the X's, I put 3, 5, 7, 9
    Can someone do this so I can see if im right with everything? I'd really appreciate it! thanks
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  2. #2
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    Quote Originally Posted by Morgan82 View Post
    I had a test today. Heres one of my questions. Can someone do it, because im not sure if I got it right, and I'd like to know now.

    You have two different dice. One die has a 1 and five 3's.
    The next die has four 2's and two 6's.

    Like this:

    Die 1- 133333
    Die 2- 222266

    Set up this table:
    X __ __ __ __
    p(X) __ __ __ __

    What is the mean?
    What is the standard deviation?

    For the X's, I put 3, 5, 7, 9
    Can someone do this so I can see if im right with everything? I'd really appreciate it! thanks
    So X is the random variable the sum of the total of the two dice?

    Looking at the sample space and using (number of favourable outcomes)/(total number of outcomes), it's not hard to see that

    Pr(X = 3) = 4/36 = 1/9.
    Pr(X = 5) = 20/36 = 5/9.
    Pr(X = 7) = 2/36 = 1/18.
    Pr(X = 9) = 10/36 = 5/18.

    Get mean and sd in the usual way.
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  3. #3
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    Quote Originally Posted by mr fantastic View Post
    So X is the random variable the sum of the total of the two dice?

    Looking at the sample space and using (number of favourable outcomes)/(total number of outcomes), it's not hard to see that

    Pr(X = 3) = 4/36 = 1/9.
    Pr(X = 5) = 20/36 = 5/9.
    Pr(X = 7) = 2/36 = 1/18.
    Pr(X = 9) = 10/36 = 5/18.

    Get mean and sd in the usual way.

    Thanks alot! Thats how I did it, now I feel alot better. Thanks again!
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