flipping a coin (similar to the ballot problem)
1. The problem statement, all variables and given/known data
You flip a coin n times. The probabilty of getting a head on any flip is p. What is the probability that the number of heads flipped is always greater than the number of tails flipped? 3. The attempt at a solution For example, if n=1, the only possibility is H if n=2, the only possibility is HH if n=3, the two possibilities are HHH or HHT if n=4, the three possibilites are HHHH, HHHT, or HHTH if n=5, the six possibilites are HHHHH, HHHHT, HHHTT, HHHTH, HHTHH, and HHTHT Of course you could keep doing this until you notice a pattern, take a guess at the formula, and then try to prove that forumula by induction. (I tried that approach but didn't get anywhere). Conditioning on the first flip clearly won't simplify the problem, and conditioning on the (n1) flip or the nth flip doesn't seem to simplify matters either. I'm stumped. 
Re: flipping a coin (similar to the ballot problem)
There's more possibility to n=3 and n=4 isnt it?
HHH, HHT, HTH, THH? 
Re: flipping a coin (similar to the ballot problem)
Quote:

Re: flipping a coin (similar to the ballot problem)
I'll tell you where I am so far. Let H(n,k) be the number of good sequences of length n (where heads lead all the time) and k is number of headsnumber of tails. You can just define H(n,k)=0 if k>n or k<=0. Ok, so far? Write a recursion relation for H(n+1,k) in terms of H(n,...). That's easy. Now take the whole list [H(n,n),H(n,n1)...H(n,1)] and figure out how to use it to construct the list [H(n+1,n+1),H(n+1,n),...,H(n+1,1)]. It's pretty easy. You just take the original list, chop off a bit, add some zeros in two different ways and add them. That let's you write a really simple computer program to compute the H(n+1) list from the H(n) list. That's great. Now that you have a simple way to construct the recursion you sit back an wait for your intuition to kick and tell you how to sum the whole thing up. Unfortunately, I'm still waiting. Any good ideas?

Re: flipping a coin (similar to the ballot problem)
Quote:
HINT: What type of probability distribution is this? CS 
All times are GMT 5. The time now is 09:21 AM. 
Powered by vBulletin Copyright ©2000  2014, Jelsoft Enterprises Ltd.
© 2014 Physics Forums