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Question for Krzys' Prac exam 1 Question 11

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  • Question for Krzys' Prac exam 1 Question 11

    In the solution it gives Pr(Z>=-2) = 0.9772.

    Why is it -2 rather than +2? Int he normal dist'n tables 0.9772 produces 2.0, so how would we work out that it is negative?

    Cheers,

    Miles
    Proper prior planning prevents poor performance!

  • #2
    Originally posted by mallkins
    In the solution it gives Pr(Z>=-2) = 0.9772.

    Why is it -2 rather than +2? Int he normal dist'n tables 0.9772 produces 2.0, so how would we work out that it is negative?

    Cheers,

    Miles

    Miles,

    Maybe I can answer your question, generally, u can use these formula from Normal Dist'n:

    1) Pr [Z>=x] = 1-Pr [Z<x]
    2) Pr [Z<-x] = 1-Pr [Z<x]

    Pr [Z>=-2] = 0.9772 because Pr [Z>=-2] = 1-Pr [Z<-2] = 1-(1- Pr[Z<2]) = 1-1+Pr [Z<2] = Pr [Z<2]

    Therefore, from the Normal Dist'n table, it is equal to 0.9772.

    I hope I can answer your question!! I am also working on P exam in Feb. Work hard and good luck!!

    T
    Tears stream down your face
    I promise you I will learn from my mistakes

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    • #3
      Thanks very much. That makes sense.

      Miles
      Proper prior planning prevents poor performance!

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