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Math Help - Finding Standard deviation and mean value after finding z curve areas

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    Post Finding Standard deviation and mean value after finding z curve areas

    The diameter length of contact windows used in integrated circuits is normally distributed. About 5% of all lengths exceed 3.75 micrometers and about 1% of all lengths exceed 3.85 micrometers. What is the mean value and standard deviation of the length distribution?

    I did a reverse lookup of the z values and got 2 area values for x but what do I do next? I know I should be able to plug this into an equation but I am a little confused how I am suppose to do this.... any help or explanation would be greatly appreciated.
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by cruxkitty View Post
    The diameter length of contact windows used in integrated circuits is normally distributed. About 5% of all lengths exceed 3.75 micrometers and about 1% of all lengths exceed 3.85 micrometers. What is the mean value and standard deviation of the length distribution?

    I did a reverse lookup of the z values and got 2 area values for x but what do I do next? I know I should be able to plug this into an equation but I am a little confused how I am suppose to do this.... any help or explanation would be greatly appreciated.
    remember, \displaystyle z = \frac {X - \mu}{\sigma}

    Plug in your z values and the corresponding X values. You will then have two equations with two unknowns, \displaystyle \mu \text{ and } \sigma. Solve the system simultaneously to find their values.
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