Results 1 to 2 of 2

Math Help - even and odd probability of coin

  1. #1
    Newbie
    Joined
    Aug 2008
    Posts
    9

    even and odd probability of coin

    hi,
    i am preparing for an exam and i wondered if some one could show me explicitly
    how to calculate the probability of getting an even number of heads in flipping a coin, with probability p for heads n times.
    i know i need to sum a series but i can't manage to do it well.
    something that doesn't use too advanced math.

    thanks in advance
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Dec 2009
    Posts
    3,120
    Thanks
    1
    p=probability for heads,
    n=number of throws....

    the probability of getting an even number of heads can be expressed
    by expanding the binomial,
    or logically as follows....

    even number of heads={no heads and n tails} or {2 heads and n-2 tails} or {4 heads and n-4 tails} or {6 heads and n-6 tails} or.......etc
    and we must count all the ways these pairings can occur.

    the probability is P(0H and nT)+P(2H and [n-2]T)+........

    =(1-p)^n+\binom{n}{2}p^2(1-p)^{n-2}+\binom{n}{4}p^4(1-p)^{n-4}+......
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Coin probability...
    Posted in the Statistics Forum
    Replies: 1
    Last Post: February 17th 2011, 08:08 AM
  2. coin probability
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: February 21st 2010, 08:47 AM
  3. Probability Coin Question
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: November 17th 2009, 10:49 PM
  4. coin probability
    Posted in the Statistics Forum
    Replies: 5
    Last Post: May 13th 2008, 02:11 AM
  5. fair coin probability
    Posted in the Advanced Statistics Forum
    Replies: 4
    Last Post: May 24th 2006, 02:59 PM

Search Tags


/mathhelpforum @mathhelpforum