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Geometric Distribution

  1. Mar 6, 2014 #1
    A boy is playing with a biased coin. The probabilty of obtaining a head with the coin is 0.4. Determine the probability that the boy will require at least eleven tosses before obtaining his third head.

    I have been trying but can't get it at all... Can someone please explain me how to solve this problem?
  2. jcsd
  3. Mar 6, 2014 #2
    Ignore the probability for the moment. If the third head occurs after at least eleven tosses what is the maximum number of heads that can have occurred in ten tosses?
  4. Mar 6, 2014 #3
    Well i guess the MAX is 2 and min must be zero!
    If you come to any conclusion, feel free to explain i'll be around.
  5. Mar 6, 2014 #4

    Stephen Tashi

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    Partition the event "A max of 2 heads in 10 tosses" into 3 mutually exclusive events and find their probabilities.
  6. Mar 6, 2014 #5

    Ray Vickson

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    What does this mean? PF rules forbid us from solving your problem for you. In fact, you are supposed to show your work first before getting any help.
  7. Mar 21, 2014 #6
    No worries, i finally got a hang of this problem. Thanks for all your help.
    Well PF actually forbade you guys to solve the problem because it was in the wrong section,i'm new to the forum and am still getting used to it.
    By the way about showing my work, what if i didn't really understand the problem and needed someone to help me understand it, PF would not allow it?
  8. Mar 21, 2014 #7


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    PF rules require you to do some legwork before you can get help here. Chances are you already have, but you need to tell us what you've been thinking. It's not okay to simply say "I don't get it." That's really kind of lazy. What is it specifically that's confusing you? For example, do you not understand the problem statement? Or do you think a certain distribution applies but you don't know how to determine some parameter you need? You need to formulate a specific question.

    If you're really at a point where you can't do the above, PF isn't the place for you yet. You shouldn't even be attempting the problem because you don't know the basic material. PF isn't here so students can avoid reading their book, etc.

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