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Thread: Normal distribution Problem

  1. #1
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    Normal distribution Problem

    The height of students in a college is normally distibuted with mean,$\displaystyle \mu$ cm and standart deviation of 12 cm.Given the percentage of students with the height of less than 150 cm is 25%.Find the value of $\displaystyle \mu$

    i get:

    $\displaystyle z = \frac{X - \mu}{\sigma}$

    $\displaystyle 0.25 = \frac{150 - \mu}{12}$

    $\displaystyle \mu = 147$

    is that my answer correct?
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  2. #2
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    Quote Originally Posted by mastermin346 View Post
    The height of students in a college is normally distibuted with mean,$\displaystyle \mu$ cm and standart deviation of 12 cm.Given the percentage of students with the height of less than 150 cm is 25%.Find the value of $\displaystyle \mu$

    i get:

    $\displaystyle z = \frac{X - \mu}{\sigma}$

    $\displaystyle 0.25 = \frac{150 - \mu}{12}$

    $\displaystyle \mu = 147$

    is that my answer correct?
    0.25 is a probabilty, not the value of z. More specifically, $\displaystyle \Pr(Z < z*) = 0.25$. So $\displaystyle z* = \frac{150 - \mu}{12}$. Your job is to get the value of z* using your tables, substitute it and then solve for $\displaystyle \mu$.
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