My Math Forum  

Go Back   My Math Forum > High School Math Forum > Probability and Statistics

Probability and Statistics Basic Probability and Statistics Math Forum


Thanks Tree1Thanks
  • 1 Post By Maschke
Reply
 
LinkBack Thread Tools Display Modes
June 12th, 2017, 02:04 AM   #1
Newbie
 
Joined: Dec 2016
From: A place called UNIVERSE

Posts: 8
Thanks: 0

Conditional probability

A double headed, a double tailed and an ordinary coin are placed in a tin can. One of the coins is randomly chosen without identifying it. the coin is tossed and falls "heads". Determine the probability that the coin is the double header.
HTsds is offline  
 
June 12th, 2017, 10:34 AM   #2
Senior Member
 
Joined: Aug 2012

Posts: 1,414
Thanks: 342

I say 2/3. Here is my reasoning. I'm sure there's a formal way to do this but I never learned basic probability theory so I just cranked out the possibilities.

First, there are three coins labeled HH, TT, and TH. Note that these are just the names of the coins.

Now if you pick HH, there are two possible flip outcomes: H or H (here H and T refer to outcomes).

If you pick TT, there are two possible outcomes: T and T

If you pick TH, there are two possible outcomes: T or H.

Now we have six possible outcomes of a choice followed by a flip. Three are heads and three are tails.

Out of the three heads outcomes, two of them came from the HH choice; and one from the TH choice. Therefore the odds are 2/3 that the original flip was from the double-headed coin.

What say you, probability experts?

Code:
  
        HH         TT      TH
          |           |         |
        -----     -----    -----
        |    |     |    |    |    |
        H   H    T    T   T    H
        ^   ^                    ^
        1    2                    3

Last edited by Maschke; June 12th, 2017 at 10:40 AM.
Maschke is online now  
June 12th, 2017, 11:32 AM   #3
Newbie
 
Joined: Dec 2016
From: A place called UNIVERSE

Posts: 8
Thanks: 0

Well thank u so much , u reached the right conclusion .... thanks for the help genius !
HTsds is offline  
June 12th, 2017, 01:26 PM   #4
Senior Member
 
Joined: Aug 2012

Posts: 1,414
Thanks: 342

Quote:
Originally Posted by HTsds View Post
Well thank u so much , u reached the right conclusion .... thanks for the help genius !
Thanks much for the compliment. I'm no genius, just a guy who can count to six. Of course counting to six is harder than it looks. See Some thoughts on the number 6 by John Baez.
Thanks from greg1313
Maschke is online now  
Reply

  My Math Forum > High School Math Forum > Probability and Statistics

Tags
conditional, probability



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
conditional probability Jaket1 Probability and Statistics 1 January 29th, 2017 09:19 AM
conditional probability :( Carina Probability and Statistics 1 October 16th, 2014 07:11 AM
Conditional Probability Avocado Probability and Statistics 2 April 19th, 2014 12:36 PM
Conditional Probability stewie griffin Advanced Statistics 0 March 16th, 2010 09:18 AM
Conditional Probability (ii) naspek Algebra 0 December 16th, 2009 06:01 PM





Copyright © 2017 My Math Forum. All rights reserved.