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Probability Formula?

Discussion in 'Online Casinos' started by humannn, Mar 20, 2006.

    Mar 20, 2006
  1. humannn

    humannn Dormant account

    Hi Everyone:

    I'd like to know the formula for figuring out the probability of getting an X number of "tails" in a row (e.g. you have a 4 percent chance of flipping tails five times in a row). But what does the math actually look like?

    I used a coin as an example, but it could also apply to Craps, Roulette, Blackjack, etc.

    Thank you.
  2. Mar 20, 2006
  3. GrandMaster

    GrandMaster Ueber Meister CAG

    Mathematician by day, online gambler by night.
    If the probability of an event is p, then the probability of it happening n times in a row is p^n (p to the power of n). In the case of a coin toss, p=1/2, so the probability of 5 tails in a row is 1/2^5=1/32=0.03125=3.125%.
    4 people like this.
  4. Mar 21, 2006
  5. humannn

    humannn Dormant account

    Thank you for the answer, GrandMaster.

    So the 3.125% figure would be the odds of flipping tails 5 times in a row out of only 5 total flips, correct? Slim odds, indeed. Do you know how to figure out how many times 5 in a row would occur in an x number of flips? Say 100?
  6. Mar 22, 2006
  7. Zoozie

    Zoozie Ueber Meister CAG PABnonaccred

    Software Developer

    You need to specify this a little more precise. Do you mean flip a coin 100 times and then count number of times you have 'blocks' with TTTTT
    If you hit 10 T's in a row, do this only count as 1 or actually as 5? What if you hit 7 T's in a row etc.

    Maybe you mean the following: what is the probability that 5 T's will occur (once or more) in a row when you flip a coin 100 times.
    I ran a simulation for this problem and it gave:

    total number of succes:9721241
    total game starts:12000000 (I ran 12M simulations each of flipping a coin 100 times)
    Probability:0.8101 (81.01%)

    I can change the following parameters if this simulation is usefull to anyone.
    I generalized it to throwing a n-sided dice and counting the max number instead of flipping a coin. The problem seems hard to solve excact with math, so it was
    much faster to just simulate it.


    1 person likes this.

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