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Math Help - normal distribution question

  1. #1
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    normal distribution question

    A machine is set to manufacture circular metal discs of diameter 10 cm; in fact, the diameter (in cm) of the discs it produces is a random variable Y with normal distribution having a mean of 10.05 and a standard deviation of 0.10.
    The demand of quality control place "acceptable limits between 9.90 cm and 10.20 cm; all disks out of this range are rejected.

    a) Given that a particular disk is accepted, find the probability that its diameter is more than 10 cm.

    b) It is decided that too many discs are rejected by the standard. If a new rejection rate is to be 10%, find the new acceptable limits, equally spaced on either side of the mean.

    c) Use the fact that Var(Y) =E(Y^2) - [E(Y)]^2 to estimate the mean area of the discs.
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  2. #2
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    a) <br /> <br />
P\left(10 \leq X \leq 10.20\right) ?<br /> <br />

    b) <br />
P\left(A \leq X \leq B \right) = 0.9 ?<br />
    Where 10.05 - A = B - 10.05
    Last edited by dkmathguy; April 15th 2010 at 01:29 AM.
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