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Homework Help: Probability Distribution

  1. Oct 9, 2012 #1
    1. The problem statement, all variables and given/known data
    Consider the experiment of tossing a fair coin 4 times. What is the probability distribution of the number X of heads?

    3. The attempt at a solution
    I got (0.5)(0.5)(0.5)(0.5) = 0.0625 but its wrong and I don't know why
  2. jcsd
  3. Oct 9, 2012 #2


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    What you have calculated there is the probability of 4 heads, which is also the probability of zero heads (4 tails).

    What is the probability of 3 heads? 2 heads, etc. ?
  4. Oct 9, 2012 #3

    Ray Vickson

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    Write out in detail the "sample space" of the experiment (it will have 16 points). Count the number of heads for each of the 16 points. How many points are there in the event {2 heads}? What about for 1 head? For 3 heads?

  5. Oct 9, 2012 #4


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    In other words, the problem asked for the probability distribution, not just the probability of four heads. You also need P(three heads), P(two heads), P(one head), and P(no heads).
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