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Thread: Find the standard deviation given the mean and a probability value

  1. #1
    Newbie feli3105's Avatar
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    Find the standard deviation given the mean and a probability value

    Given $\mu=19$ and $P(Y<22.5)=0.63683$, find $\sigma$.

    I did the following:

    $$Z=\frac{Y-\mu}{\sigma}$$

    $$\sigma=\frac{Y-\mu}{Z}$$

    Then I went to the normal table to find that $P(Z<0.35)=0.63683$

    $$\sigma=\frac{Y-\mu}{Z}=\frac{22.5-19}{0.35}=10$$

    What do you think?
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  2. #2
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    Re: Find the standard deviation given the mean and a probability value

    correct
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