
Probability and Statistics Basic Probability and Statistics Math Forum 
 LinkBack  Thread Tools  Display Modes 
October 6th, 2013, 01:02 PM  #1 
Newbie Joined: Oct 2013 Posts: 3 Thanks: 0  Probability of getting an even number of tails for x throws?
Need help with the formula to calculate the probability for getting an even amount of tails after (0,1,2,...,491) coin flips. would be very thankfull for some help 
October 6th, 2013, 03:09 PM  #2 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond  Re: Probability of getting an even number of tails for x thr
If zero is considered even, the probability of getting an even number of tails on zero coin tosses is 1 and the probability of getting an even number of tails on every other number of tosses is 1/2.

October 6th, 2013, 03:17 PM  #3 
Newbie Joined: Oct 2013 Posts: 3 Thanks: 0  Re: Probability of getting an even number of tails for x thr
well i know the probabilityis 1/2 but i think i need to do an binomial of it because i need to figure out the probability of getting a even number of tails in say 491 coin flips

October 6th, 2013, 03:19 PM  #4 
Newbie Joined: Oct 2013 Posts: 3 Thanks: 0  Re: Probability of getting an even number of tails for x thr
only well motivated answers are accepted

October 6th, 2013, 04:06 PM  #5 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond  Re: Probability of getting an even number of tails for x thr
There are 2^n possible outcomes, 2^(n  1) of which have an even number of tails. 2^(n  1)/2^n = 1/2.

October 6th, 2013, 04:56 PM  #6 
Global Moderator Joined: May 2007 Posts: 6,806 Thanks: 716  Re: Probability of getting an even number of tails for x thr
You could use mathematical induction on the number of tosses if you want a formal proof.

October 6th, 2013, 05:23 PM  #7  
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1038  Re: Probability of getting an even number of tails for x thr Quote:
 

Tags 
number, probability, tails, throws 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Getting sum of 6 in at least three throws  0mar_little  Advanced Statistics  2  October 15th, 2013 05:29 PM 
Effects of Clustering of Heads or Tails  coolcat  Advanced Statistics  1  November 27th, 2011 11:03 PM 
toss coin until the first run of r consecutive tails occurs  johnmath  Advanced Statistics  6  July 1st, 2010 11:49 PM 
Probabilty of consecutive heads/tails in weighted coin toss  slyone  Algebra  2  September 5th, 2008 04:05 PM 
Probabilty of consecutive heads/tails in weighted coin toss  slyone  Advanced Statistics  1  September 4th, 2008 06:13 AM 