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Math Help - stand norm rand var

  1. #1
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    stand norm rand var

    if X~N(-10,25) Find x such that P(X<x)=1/10
    i could not find any Ix on the statistical table with value 0.1 so i am stuck,what intermiediate step should i take?
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  2. #2
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    Quote Originally Posted by math8553 View Post
    if X~N(-10,25) Find x such that P(X<x)=1/10
    i could not find any Ix on the statistical table with value 0.1 so i am stuck,what intermiediate step should i take?
    If instead it asked for x such that P(X<x)=9/10 would that help.

    .
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  3. #3
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    Quote Originally Posted by Constatine11 View Post
    If instead it asked for x such that P(X<x)=9/10 would that help.

    .

    Not really sure what the answer is to this question. Can someone please confirm this. I got two different answer but not sure which one is correct.

    1) z = -1.282 (from normal table)

    x = z(sigma) + mu = -1.282(5) + -10 = -16.41


    2)z = 1.282 (from normal table)

    x = z(sigma) + mu = 1.282(5) + -10 = -3.59

    Please cans some1 tell me which 1 is correct thanks
    Last edited by 1234567; January 13th 2009 at 12:51 PM.
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  4. #4
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    Quote Originally Posted by 1234567 View Post
    Not really sure what the answer is to this question. Can someone please confirm this. I got two different answer but not sure which one is correct.

    1) z = -1.282 (from normal table)

    x = z(sigma) + mu = -1.282(5) + -10 = -16.41


    2)z = 1.282 (from normal table)

    x = z(sigma) + mu = 1.282(5) + -10 = -3.59

    Please cans some1 tell me which 1 is correct thanks
    X = -16.41 is the answer to the question you originally asked. X = -3.59 was a means of getting that answer.
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  5. #5
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    Quote Originally Posted by mr fantastic View Post
    X = -16.41 is the answer to the question you originally asked. X = -3.59 was a means of getting that answer.

    so does this mean for x must be = -16.41
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    Quote Originally Posted by 1234567 View Post
    so does this mean for x must be = -16.41
    Quote Originally Posted by mr fantastic View Post
    X = -16.41 is the answer to the question you originally asked. [snip]
    ..
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  7. #7
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    Quote Originally Posted by mr fantastic View Post
    ..

    Thank you for clearing it up for me, i wasn't to sure about it.
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