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Math Help - Normal Distribution question

  1. #1
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    Normal Distribution question

    Hi
    Can someone help me on the following questions:
    Determine the value of z in the following case: Pr(-z<Z<z)=0.954

    I done InvNorm(0.954,0,1) but this is incorrect


    Find the quartiles of the standard normal distribution?

    P.S
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  2. #2
    Senior Member BAdhi's Avatar
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    Re: Normal Distribution question

    first find the \textrm{P}(Z<z)

    it will be equal to \frac{0.954}{2}+0.5=0.977

    so find z according to that value from the data sheet
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  3. #3
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    Re: Normal Distribution question

    Quote Originally Posted by BAdhi View Post
    first find the \textrm{P}(Z<z)

    it will be equal to \frac{0.954}{2}+0.5=0.977
    why do you have to plus 0.5 after halving 0.954?
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  4. #4
    Senior Member BAdhi's Avatar
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    Re: Normal Distribution question

    because normally on datasheets, \textrm{P}(Z<z) is given,

    so after halving 0.954 you'll get \textrm{P}(0<Z<z). In order to get the above value you should add 0.5 (because the graph is symmetrical around P(z) axis)
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  5. #5
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    Re: Normal Distribution question

    How would i find the quartiles of the standard normal distribution?

    i know that there it is split into three sections, but how do i calculate the percentages
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  6. #6
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    Re: Normal Distribution question

    Quote Originally Posted by Paymemoney View Post
    How would i find the quartiles of the standard normal distribution?

    i know that there it is split into three sections, but how do i calculate the percentages
    Rview the definition of a quartile. Then apply what you learned so far in this thread.
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