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Probability of expected size

  1. Mar 17, 2009 #1
    X is the number of girls in a one-boy family, and so X+1=the size of a one-boy family. What is the expected size of a one-boy family in terms of [tex]\alpha[/tex]? What is the expected size of a one-boy family if [tex]\alpha[/tex]=0.51?

    [tex]\alpha[/tex]=the probability that a random birth is a boy

    I know this isn't difficult, but the terminology has completely gotten me confused. How do I solve for this with an actual formula?
  2. jcsd
  3. Mar 17, 2009 #2
    Would this be equivalent to:

    [tex]E[X]=\alpha + (1- \alpha) \times x [/tex]
  4. Mar 17, 2009 #3
    What is a one-boy family? How can there be girls in a one-boy family?
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