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Math Help - Mean/variance of random variable...hmmmm

  1. #1
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    Red face Mean/variance of random variable...hmmmm

    So here is the problem:

    " The mean of a random variable, x, is 19 and its variance is 5. What is the mean, variance and standard deviation of y where y=7x-2? "

    I'm new to random variable statistics, so I'm having trouble understanding how a variable x can have a mean and a variance...

    Thanks!
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  2. #2
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    Quote Originally Posted by trank31337 View Post
    So here is the problem:

    " The mean of a random variable, x, is 19 and its variance is 5. What is the mean, variance and standard deviation of y where y=7x-2? "

    I'm new to random variable statistics, so I'm having trouble understanding how a variable x can have a mean and a variance...

    Thanks!
    If the random variable X has mean \mu and variance \sigma^2, then the random variable Y = aX + b has mean a \mu + b, variance a^2 \sigma^2 and standard deviation |a| \sigma.

    In your question a = 7 and b = -2.
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