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Math Help - Stats: probability and zscores help

  1. #1
    Member cmf0106's Avatar
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    Stats: probability and zscores help

    Im looking back over an old assignment and I cant figure out how to get the correct probability

    Question: what is the probability of encountering a state with annul income less than ore equal to Maine?

    Maine: (19590- 21856)/3537.59= - .64
    (Maines income - mean) / standard deviation

    go to the ztable, and the area associated with -.64 is .2611

    then somehow I came up with a probability value of 26.43%, which is the correct answer but I have no idea how to get this probability value.

    Please help
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  2. #2
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    mr fantastic's Avatar
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    Quote Originally Posted by cmf0106 View Post
    Im looking back over an old assignment and I cant figure out how to get the correct probability

    Question: what is the probability of encountering a state with annul income less than ore equal to Maine?

    Maine: (19590- 21856)/3537.59= - .64
    (Maines income - mean) / standard deviation

    go to the ztable, and the area associated with -.64 is .2611

    then somehow I came up with a probability value of 26.43%, which is the correct answer but I have no idea how to get this probability value.


    Please help
    Pr(Z < -0.64) = Pr(Z > 0.64) = 1 - Pr(Z < 0.64) = 0.2611. I assume you got Pr(Z < 0.64) from tables ......

    To get a percentage, mutiply by 100.

    I don't know where 26.43% has come from .....
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