My Math Forum  

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

Probability and Statistics Basic Probability and Statistics Math Forum


Reply
 
LinkBack Thread Tools Display Modes
July 3rd, 2011, 01:01 PM   #1
Newbie
 
Joined: Jun 2011

Posts: 9
Thanks: 0

Probability Question

If Pr[E] = 1/4 and Pr[F] = 1/5

If it is known that when event F occurs, event E is 3 times more likely to occur than not to occur, find Pr[Fc | Ec].

Do we have to show that event E is 3 times likely to occur than not to occur even though when we are finding Pr[Fc | Ec] and event F doesn't occur?

Also how do we go about solving this question?

Thanks!
Azntopia is offline  
 
July 3rd, 2011, 01:35 PM   #2
Newbie
 
Joined: Jun 2011

Posts: 9
Thanks: 0

Re: Probability Question

Also if two events are mutually exclusive, is it possible for neither of them to occur? I know that they both can't occur at the same time.

Once again, thanks!
Azntopia is offline  
July 3rd, 2011, 03:10 PM   #3
Senior Member
 
mrtwhs's Avatar
 
Joined: Feb 2010

Posts: 706
Thanks: 141

Re: Probability Question

Quote:
Originally Posted by Azntopia
If Pr[E] = 1/4 and Pr[F] = 1/5

If it is known that when event F occurs, event E is 3 times more likely to occur than not to occur, find Pr[Fc | Ec].





mrtwhs is offline  
July 3rd, 2011, 06:56 PM   #4
Senior Member
 
Joined: Apr 2011
From: USA

Posts: 782
Thanks: 1

Re: Probability Question

I went about this a completely different way, but got the same answer. So to answer your other questions:

Quote:
Originally Posted by Azntopia
Do we have to show that event E is 3 times likely to occur than not to occur even though when we are finding Pr[Fc | Ec] and event F doesn't occur?
You'd need to know that P(E|F) = 3/4 so that it sets up the relationship between these dependent events. You're able to get other info from that. Many times you have to use the info given to "back into" other stuff. If you're stuck on something like this, then write down everything you do know, and write down the equations you need, fill in what you have, and then see what is missing. You may be able to solve one thing, and use that to plug in elsewhere, or use algebra to solve for some missing number, etc.

Quote:
Also if two events are mutually exclusive, is it possible for neither of them to occur?
Yes, assuming the two don't already add up to 1. Like if there's a .70 probability you will drive your car to work, and a .05 probability you will ride your bike, there's still a .25 probability you will do neither and use some other method. Being mutually exclusive just means there's no intersection - both can't happen (also making them dependent), but it doesn't prevent the "neither" option.
Erimess is offline  
July 4th, 2011, 05:47 AM   #5
Newbie
 
Joined: Jun 2011

Posts: 9
Thanks: 0

Re: Probability Question

Thank you so much mrtwhs and Erimess! This really helped me understand these type of probability questions and I was able to solve the rest of them fairly easily by understanding how you guys approached it.
Azntopia is offline  
Reply

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

Tags
probability, question



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Probability Question jskrzy Probability and Statistics 4 October 31st, 2011 02:11 PM
Probability Question skate_rds Advanced Statistics 3 March 17th, 2011 07:37 AM
Another Probability Question skate_rds Advanced Statistics 0 February 6th, 2011 09:16 PM
Probability question madflame991 Probability and Statistics 0 February 1st, 2011 01:06 AM
Probability question tnutty Advanced Statistics 1 January 27th, 2011 04:31 PM





Copyright © 2019 My Math Forum. All rights reserved.