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Homework Help: Bernoulli trials

  1. Oct 28, 2009 #1
    say you perform one bernoulli experiment where outcome X = 0 and X=1 are failure and success, respectively. then you have P(X=0) = 1-p and P(X=1) = p.

    what if you expand this to two bernoulli experiments? only 1/4 cases would be successful, so you would have:

    P(X=1) = p^2
    E(X) = p^2
    Var(X) = ?

    i'm hung up on how to calculate Var(X). any thoughts?
  2. jcsd
  3. Oct 29, 2009 #2


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    Staff Emeritus
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    1/4 cases are successful if you define success to be two consecutive trials in a row succeed. In this case you just have a single Bernoulli trial with probability of success p2. So just take the formula for the variance of a Bernoulli trial and plug in p2
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