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Math Help - Normal distribution

  1. #1
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    Normal distribution

    I have a question about how to show the work for this and how to solve it also
    Here is the problem:
    The verbal part of the GRE has a mean of 500 and a standard deviation of 100. Use the normal distribution to answer the questions:
    a. if we wanted to select only students at or above the 90th percentile, what verbal gre score would we use as a cutoff? I got the answer 628.01 but unsure about how to show my work
    b.what verbal gre score corresponds to a percentile rank of 15%. 55%?
    c what is the precentile rank of a verbal gre score of 628? 350?
    d if we randomly selcted 1,500 students who had taken the verbal gre how many would we expect to score lower than 250? higher than 750?
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  2. #2
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    Re: Normal distribution

    For he first one...

    \displaystyle P\left( Z> \frac{x-500}{100}\right) = 0.9
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    Re: Normal distribution

    how would that be worked out?
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  4. #4
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    Re: Normal distribution

    In the normal distribution table, find the value of \displaystyle Z_0 such that


    \displaystyle P\left( Z> Z_0) = 0.9

    Make the result equal to \displaystyle \frac{x-500}{100} and solve for x
    Last edited by pickslides; October 3rd 2011 at 01:29 PM. Reason: sp
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