# S.O.S. Mathematics CyberBoard

Your Resource for mathematics help on the web!
 It is currently Sat, 18 May 2013 11:21:34 UTC

 All times are UTC [ DST ]

 Page 1 of 1 [ 2 posts ]
 Print view Previous topic | Next topic
Author Message
 Post subject: Word problem with probabilities and averagesPosted: Tue, 15 Nov 2011 09:01:50 UTC
 S.O.S. Newbie

Joined: Tue, 15 Nov 2011 08:59:57 UTC
Posts: 1
I have four scenarios with five rounds each where an event x, y, or z will be chosen.

In the first scenario, each round has a equal chance of triggering event x and will continue triggering event y each round until event x is triggered. Example1: if event x is triggered on r1, y=0. Example2: if event x is triggered on r3, y=2. Example3: if event x is triggered on r5, y=4.

In the second scenario, each round has a 20% chance of triggering event x and will continue triggering event y each round until event x is triggered. Example: event x is triggered on r1, y=0. Example2: event x is triggered on r4, y=3. Example3: event x is never triggered, y=5.

In the third scenario, each round has a 75% chance of triggering event x and if it is not triggered that round it will trigger event y. Example1: event x is triggered every round, y=0. Example2: event x is triggered on rounds 1,2,and 5, y=2. Example3: event x is triggered on rounds 3 and 4, y=3.

In the fourth scenario, rounds 1 through 4 each have a equal chance of triggering event x. Each round x has not been triggered, there is a 50% chance that event y will trigger else event z will trigger. Once x has been triggered, event y will not trigger. Example1: event x triggers on round 1, y=0. Example2: event x triggers on round 4, y triggers on round 1 and 3, y=2.

I am trying to learn how to calculate the average on the amount of times event y will trigger in each scenario based on the probabilities given in each scenario. I took calculus in high school so I am a little rusty on my math, but if someone explained it I would understand.

Here are my attempts:

Scenario #1
If each round has an equal chance of triggering event x, and there are five rounds, that would mean that each has a 20% chance to trigger. So I would think the formula would be:
((.2*0)+(.2*1)+(.2*2)+(.2*3)+(.2*4))/5 = 40% chance to trigger y each round

Scenario #2
I am not sure how to do this one as it should be different from scenario 1, and I think I messed up on scenario 1.

Top

 Post subject: Re: Word problem with probabilities and averagesPosted: Wed, 7 Dec 2011 18:42:49 UTC
 Member of the 'S.O.S. Math' Hall of Fame

Joined: Tue, 20 Nov 2007 04:36:12 UTC
Posts: 826
Location: Las Cruces
lisaburlew wrote:
I have four scenarios with five rounds each where an event x, y, or z will be chosen.

In the first scenario, each round has a equal chance of triggering event x and will continue triggering event y each round until event x is triggered. Example1: if event x is triggered on r1, y=0. Example2: if event x is triggered on r3, y=2. Example3: if event x is triggered on r5, y=4.

Your description of the problem is unclear. If y is an event, what kind of event is it? Is it something that either happens or doesn't? If that is the case, why do you give an example with y = 4? Are you using "y" to denote both the event and the total number of times that it happened? (If so, stop doing that!) Are x,y and z mutually exclusive events? Or is it the case that several of these events can happen on the same round?

Quote:

I am trying to learn how to calculate the average on the amount of times event y will trigger in each scenario

It isn't clear what you count as a "time". Does event y happen or not happen on each round? If it happens on rounds 2,4 and 5, do you count that as three times that it happened? -or do you count that as one time since it did happen at least once in the scenario?

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 2 posts ]

 All times are UTC [ DST ]

#### Who is online

Users browsing this forum: No registered users

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forum

Search for:
 Jump to:  Select a forum ------------------ High School and College Mathematics    Algebra    Geometry and Trigonometry    Calculus    Matrix Algebra    Differential Equations    Probability and Statistics    Proposed Problems Applications    Physics, Chemistry, Engineering, etc.    Computer Science    Math for Business and Economics Advanced Mathematics    Foundations    Algebra and Number Theory    Analysis and Topology    Applied Mathematics    Other Topics in Advanced Mathematics Other Topics    Administrator Announcements    Comments and Suggestions for S.O.S. Math    Posting Math Formulas with LaTeX    Miscellaneous