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Chances of landing 9 tails in a row? watch

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    Having an argument with a friend about the odds/chances of it happening. Given that it's a 50/50 chance of heads/tails what would the odds of landing 9 tails in a row be? Expressed as a fraction
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    (\frac{1}{2})^{9}, no?

    I always have sucked at probability, though.
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    I have no calculator handy...  .5^9
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    (Original post by ashy)
    (\frac{1}{2})^{9}, no?

    I always have sucked at probability, though.
    I know how you feel. I havn't done stats in a month and for a second Poisson flashed through my mind...
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    Yeh it's just (1/2)^9, which is 1/(2^9) which is 1/512.
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    (Original post by impervious)
    I have no calculator handy...  .5^9
    Calculator? 1/512 :p:
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    Calculator - why? Its 1 in 512. Edit: damn my slowness in typing
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    (Original post by impervious)
    I know how you feel. I havn't done stats in a month and for a second Poisson flashed through my mind...
    I have a physics degree, and for a brief moment the binomial expansion drifted through my mind. Why? Stupid brain.
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    (Original post by rnd)
    Calculator? 1/512 :p:
    Not so hot at mental maths.. and I wasn't thinking :P You wouldn't believe me if I said I took further maths would you?
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    (Original post by impervious)
    Not so hot at mental maths.. and I wasn't thinking :P You wouldn't believe me if I said I took further maths would you?
    Course I would.

    I'm not much good a mental maths either but I've accidentally memorised quite a lot of useful stuff including powers of 2.
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    The probabillity of getting 9 tails in a row is the same as getting 5 heads and 4 tails.

    Coins don't have memory of what side it has landed on.

    P.S. Thats not including the probability that it lands on the edge.
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    (Original post by Simplicity)
    The probabillity of getting 9 tails in a row is the same as getting 5 heads and 4 tails.

    Coins don't have memory of what side it has landed on.

    P.S. Thats not including the probability that it lands on the edge.
    But do you know the probability of a given sized coin landing on its edge? :p:.
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    (Original post by Simplicity)
    The probabillity of getting 9 tails in a row is the same as getting 5 heads and 4 tails.

    Coins don't have memory of what side it has landed on.

    P.S. Thats not including the probability that it lands on the edge.
    The probability of getting 5 heads and 4 tails is:

    9C4 multiplied by 0.5^9 = 126/512 = 63/256




    Thats because there are 126 different ways in which you can get 5 heads and 4 tails, and only one way in which you can get 9 tails. Of course, the probability of getting 5 heads and 4 tails is the same (1/512)
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    (Original post by little_wizard123)
    But do you know the probability of a given sized coin landing on its edge?
    I think the main thing is the spin of the coin and not the size. Also, the weight of the coin.
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    (Original post by Simplicity)
    The probabillity of getting 9 tails in a row is the same as getting 5 heads and 4 tails.
    Actually, the probability of getting 5 heads and 4 tails is 126 times larger than the probability of getting 9 tails.

    If you had said "the probability of getting 5 heads followed by 4 tails", you would have a point.
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    Thats what I meant:o:
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    (Original post by Simplicity)
    I think the main thing is the spin of the coin and not the size. Also, the weight of the coin.
    Sorry, I meant size as "would you know the probability of a 2p coin landing on its side". It was more of a joke really.
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    What I thought =]
    Thanks guys.
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    To be fair if a human flips a coin it will biased a bit towards heads. So the probability of flipping a coin and it landing on heads is not 50% more like 51%.
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    (Original post by Simplicity)
    To be fair if a human flips a coin it will biased a bit towards heads. So the probability of flipping a coin and it landing on heads is not 50% more like 51%.
    Why?
 
 
 
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