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Math Help - Upper Quartile & Lower Quartile

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    Upper Quartile & Lower Quartile

    The distribution of the birth weights of babies delivered at 40 weeks is approximately normal with a mean of 3500g and standard deviation of 430g.

    Calculate the upper quartile of birth weight. What is the lower quartile?
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    Quote Originally Posted by brumby_3 View Post
    The distribution of the birth weights of babies delivered at 40 weeks is approximately normal with a mean of 3500g and standard deviation of 430g.

    Calculate the upper quartile of birth weight. What is the lower quartile?
    Upper quartile:

    You need to solve Pr(X > x) = 0.25 for x.

    To do this, first find the value of z* such that Pr(Z > z*) = 0.25.

    Now note that z* = \frac{x - 3500}{430} and solve for x.

    ----------------------------------------------------------------------------------

    Lower quartile is done the same way.
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