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Math Help - Normal Distrbution , how to find sign of z

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    Normal Distrbution , how to find sign of z

    In a normal Distribution 31% of the item are under 45 and 8 % are above 64.Find its mean and SD?
    In a normal Distribution 31% of the item are under 45 and 8 % are above 64.Find its mean and SD
    My doubt is how to know if z < 0 or >0 .
    I really need to understand the concept behind taking z1. What does 31 % indicate? negative as it is below 50 % ? Somebody please help me.I'm badly in need of a way to solve this problem
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    Re: Normal Distrbution , how to find sign of z

    Quote Originally Posted by jeevanbmanoj View Post
    In a normal Distribution 31% of the item are under 45 and 8 % are above 64.Find its mean and SD?
    In a normal Distribution 31% of the item are under 45 and 8 % are above 64.Find its mean and SD
    My doubt is how to know if z < 0 or >0 .
    I really need to understand the concept behind taking z1. What does 31 % indicate? negative as it is below 50 % ? Somebody please help me.I'm badly in need of a way to solve this problem
    Pr(Z < 0) = 0.5. 31% is equivalent to a probability of 0.31. So what does that tell you about the z-value corresponding to 45 ....?

    Pr(Z > 0) = 0.5. So what does that tell you about the z-value corresponding to 64 ....?
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