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Q: Probability ( Answered,   1 Comment )
Subject: Probability
Category: Science > Math
Asked by: johnjri1-ga
List Price: $2.00
Posted: 24 Nov 2006 19:00 PST
Expires: 24 Dec 2006 19:00 PST
Question ID: 785371
Event 'A' has a 50% chance of ocurring.

The only way event 'B' can occur is if event 'A' occurs;
If event 'A' occurs, event 'B' has a 50% chance of occuring.

The only way event 'C' can occur is if event 'B' occurs;
If event 'B' occurs, event 'C' has a 50% chance of occuring.

What are the chances of event 'C' occuring?

I think it is 50% x 50% x 50% = 12.5%, but I am not sure that is right.
Please show your math if I am wrong.
Subject: Re: Probability
Answered By: pafalafa-ga on 21 Dec 2006 05:37 PST
Let's say the action you're talking about is a flip of the coin, and
the "event" would be the coin coming up Heads.

For the first flip, you have a %100 chance of getting to flip, and 50%
chance it comes up heads.

There's then a 50% chance of a second flip, and a 50% chance of that
being Heads -- .50 * .50 = 25%.

So...there's a 25% chance of getting to a third flip, which has a
50/50 chance of Heads -- .25 * .50 = 12.5%

As you thought, the odds are 12.5%.



Clarification of Answer by pafalafa-ga on 28 Dec 2006 10:22 PST
It dawned on me this might be some math homework for school, and that
you might like some extra help.  If so, just let me know by posting a
note, here, and I'll provide whatever math homework help I can. 
Probability is always a fascinating, but challenging topic.


Subject: Re: Probability
From: bhen_03-ga on 24 Nov 2006 19:35 PST
P(C/A?B) = 0.5

P(C) = P(A?B?C) = P(A)* P(B/A)* P(C/A?B) = 0.5*0.5*0.5
P(C) = 0.125 = 12.5%

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