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Thread: Normal distribution

  1. #1
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    Normal distribution

    Statistics help? X is distributed normally, P(x>=59.1) =0.0218 and P(x>=29.2)=0.9345 Find the mean and standard deviation of the distribution, correct to 3 significant figures.
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  2. #2
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    Re: Normal distribution

    If you are expected to do this kind of problem then you should know that, given a normal distribution with mean \mu and standard deviation \sigma, variable x corresponds to a "standard normal distribution" z= \frac{x- \mu}{\sigma}. Here, you need to look up, in a table of the standard normal distribution, z_0 corresponding to P(z\ge z_0)= 0.0218 and z_1 such that P(z\ge z_1)= 0.9345. Then, using those values for z_0 and z_1, solve the two equations z_0= \frac{59.1- \mu}{\sigma} and z_1= \frac{29.2- \mu}{\sigma} for \mu and \sigma.
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