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Math Help - Normal Probability Distribution

  1. #1
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    Normal Probability Distribution

    Suppose that a particular entrance examination into Public Service is designed so that the marks will be normally distributed with a mean of 300 and a standard deviation of 60. If only the top 15% of candidates are selected, what mark would a student be expected to obtain for admission?

    I did .5 - .15 to find the percentage that would be below top 15% in the upper half.

    =.35

    went to my normal distribution table, found 3508 (closest listed to 3500) = 1.04 Z value.

    Plugged 1.04 into z = (x - mean) / standard D

    Z x S.D. + Mean = X

    1.04 x 60 + 300 = 362.4

    x = 362.4

    Correct? Thanks in advance.
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  2. #2
    Grand Panjandrum
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    Re: Normal Probability Distribution

    Quote Originally Posted by Ploppies View Post
    Suppose that a particular entrance examination into Public Service is designed so that the marks will be normally distributed with a mean of 300 and a standard deviation of 60. If only the top 15% of candidates are selected, what mark would a student be expected to obtain for admission?

    I did .5 - .15 to find the percentage that would be below top 15% in the upper half.

    =.35

    went to my normal distribution table, found 3508 (closest listed to 3500) = 1.04 Z value.

    Plugged 1.04 into z = (x - mean) / standard D

    Z x S.D. + Mean = X

    1.04 x 60 + 300 = 362.4

    x = 362.4

    Correct? Thanks in advance.
    More or less, yes.

    CB
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