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Homework Help: Conditional normal distribution

  1. May 7, 2013 #1
    1. The problem statement, all variables and given/known data

    We have two normally distributed random variables:

    A = N(129, 29.4)
    B = N(86, 24.0)

    What is the probability A is atleast twice the size of B?

    3. The attempt at a solution

    P(A > 2B | B = b) or something? I think we are supposed to use the CLT somehow but I don't know how when it's conditional...
     
  2. jcsd
  3. May 7, 2013 #2

    Ray Vickson

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    Science Advisor
    Homework Helper

    In the notation N(a,b), is b the variance or the standard deviation? I have seen both conventions used, so you need to tell us which one you mean. Also: are A and B independent?---you need to tell us that, too.
     
  4. May 7, 2013 #3
    b is the stdev. A and B are independent. Sorry!
     
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