Previous in Forum: Software to Solve Problem of Planning and Inventory Control   Next in Forum: What Happens if Earth Stops Rotating?
Close
Close
Close
36 comments
Rating: Comments: Nested
Active Contributor

Join Date: May 2009
Posts: 15

Probability Question

04/12/2015 9:23 AM

Can anyone in this forum able to solve this pribability question? This is the challenging question and i want help frm the fotum gurus.

A player flips a fair coin and scores n points if head comes up and scores two points if tail comes up the plays till he receives n points.if Pn is the probability of getting exactly n points.

Pn=1/2 (Pn-1 - Pn-2)

Find the value of Pn?

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Good Answers:

These comments received enough positive votes to make them "good answers".

"Almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, vote them!
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#1

Re: probability question

04/12/2015 9:50 AM

We don't do homework questions here.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
2
Guru

Join Date: Mar 2007
Location: City of Light
Posts: 3943
Good Answers: 183
#2

Re: probability question

04/12/2015 9:57 AM

At 1st flip the probability is 50%.

If the 1st flip is not the right one then the first question is : is n=2*m? Then it is a possibility that a series of "wrong" flips leads to the sum=n. If n= 2*m+1 then the probability with further flips to obtain sum=n is nil.

In the case that n=2*m we can assume that the probability is 0.5^m which is the probability to have a series of flips of same value.

Register to Reply Good Answer (Score 2)
Active Contributor

Join Date: May 2009
Posts: 15
#3
In reply to #2

Re: probability question

04/12/2015 10:08 AM

Please can u explain ur answer in details

Register to Reply
Guru

Join Date: Mar 2012
Location: Out of your mind! Not in sight!
Posts: 4424
Good Answers: 108
#4
In reply to #3

Re: probability question

04/12/2015 10:15 AM

He just did!

Please do your homework and at least think through what has been said.

__________________
Common Sense Dictates
Register to Reply
Guru

Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 4496
Good Answers: 137
#7
In reply to #3

Re: probability question

04/12/2015 11:16 AM

I didn't understand it, but I didn't understand your original question either. n seems to mean different things in different places, unless I'm missing something.

__________________
Give masochists a fair crack of the whip
Register to Reply
Guru

Join Date: Feb 2011
Posts: 7025
Good Answers: 207
#5

Re: probability question

04/12/2015 10:54 AM

the probability of anyone here doing your homework is a solid ZERO

Register to Reply
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 14331
Good Answers: 162
#23
In reply to #5

Re: probability question

04/13/2015 12:43 PM

Besides the pribibility is undefined in the limits of your equation.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 33392
Good Answers: 1817
#6

Re: probability question

04/12/2015 11:13 AM
__________________
All living things seek to control their own destiny....this is the purpose of life
Register to Reply
Active Contributor

Join Date: May 2009
Posts: 15
#14
In reply to #6

Re: probability question

04/12/2015 2:15 PM

THanks for given the link for basic understsndibg if probability

Register to Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#8

Re: probability question

04/12/2015 11:54 AM

8 Top Websites that Students Use to Cheat - CBS News

DO YOUR WON HOMEWORK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

READ THE RULES for posting!!!Do your own homework. CR4 is not a homework cheat site; however, if you have questions about understanding concepts or how a portion of a problem is derived, these types of questions will be accepted.

Register to Reply
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 21017
Good Answers: 795
#10
In reply to #8

Re: probability question

04/12/2015 12:56 PM

Did CR4 make it into the eight?

__________________
In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#13
In reply to #10

Re: probability question

04/12/2015 1:57 PM

No. I think that finding CR4 requires more organizational and search skills than is possessed by the average loser who is just trying to cheat their way to an "education".

I think it's somewhat of a random happenstance that they find their way to this forum.

Once here, they seem to keep on returning to the well instead of doing their own research.

But hey, What do I know?

Register to Reply
Guru

Join Date: Sep 2012
Location: Iowa, USA
Posts: 577
Good Answers: 50
#11
In reply to #8

Re: probability question

04/12/2015 1:10 PM

The OP, Mr. Haris Aslam, graduated in 2010, as indicated in his earlier posts dating back then.

He could be working on a Masters, or PHD, but may just be curious to this probability outcome.

__________________
ignator -
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#12
In reply to #11

Re: probability question

04/12/2015 1:20 PM

Sure, I'll buy that if you'd like.

Register to Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#15
In reply to #11

Re: probability question

04/12/2015 2:22 PM
Register to Reply
Guru

Join Date: Sep 2012
Location: Iowa, USA
Posts: 577
Good Answers: 50
#16
In reply to #15

Re: probability question

04/12/2015 4:04 PM

More then one name?

Haris

Must be a text book question about an unfair coin toss.

__________________
ignator -
Register to Reply
Guru
Popular Science - Weaponology - New Member Engineering Fields - Engineering Physics - New Member Engineering Fields - Nuclear Engineering - New Member

Join Date: Dec 2007
Location: No. VA, USA (No, it does NOTu mean "won't go"!)
Posts: 1796
Good Answers: 75
#19
In reply to #11

Re: probability question

04/13/2015 12:39 AM

If he graduated, why can't he either

a) do what he learned when he got his (flaunted) degree? or

b) check the books that are too available to see what he forgot?

I'm not impressed with "he graduated" if he didn't learn how to do what he studied. What's so great about a degree that does nothing better than stick letters after your name?

We don't do homework, unless it's our own. And we don't do THAT here!!

__________________
Been away a while. Miss all my old friends. Some of you I KNOW are still around. Where are the rest?
Register to Reply
Guru

Join Date: Jul 2007
Location: Commissariat de Police, Nouvions, occupied France, 1942.
Posts: 2599
Good Answers: 77
#9

Re: probability question

04/12/2015 12:52 PM

Show your working and show you're working.

__________________
Good moaning!
Register to Reply
Anonymous Poster #1
#17

Re: Probability Question

04/12/2015 6:29 PM

I realize the pressure created by thinking of something to type when the people in line behind you and the guy peddling the bicycle generator are starting to get agitated. Perhaps it would be best if you where to return to your job of picking fly dung out of pepper and try again later.

Register to Reply Off Topic (Score 12)
Guru
Popular Science - Cosmology - Let's keep knowledge expanding Engineering Fields - Retired Engineers / Mentors - Hobbies - HAM Radio - New Member

Join Date: Dec 2006
Location: North America, Earth
Posts: 4528
Good Answers: 106
#18

Re: Probability Question

04/12/2015 11:36 PM

I probably won't answer you, and if I did, the answer would probably be wrong.

__________________
“I would rather have questions that can't be answered than answers that can't be questioned.” - Richard Feynman
Register to Reply
Guru

Join Date: Mar 2007
Location: City of Light
Posts: 3943
Good Answers: 183
#20

Re: Probability Question

04/13/2015 4:13 AM

It is quite amusing how people react to a challenge !

I introduced a flaw in my explanation but nobody made the effort to analyse the problem, the only effort was to discard any intellectual effort and say "go away with your questions we are not here to solve your problems".

In fact the reaction was exactly as I expected it is the one I see during last times.

It was different before but times change.

I expect a lot of aggressive comments but I had to say what I think as usual.

Register to Reply
Guru

Join Date: Mar 2012
Location: Out of your mind! Not in sight!
Posts: 4424
Good Answers: 108
#21
In reply to #20

Re: Probability Question

04/13/2015 5:05 AM

How do you think this goes down giving the wrong answer here?

If there is one?

50% for the first go is clear.

Multiple throws that are not head lead to n. If there is one head in the middle then it is not possible to obtain n.

So what's the catch? It is most probable that with the second throw you are off.

I toss this. OP has not come back so why bother.

I am out.

__________________
Common Sense Dictates
Register to Reply
Guru

Join Date: Mar 2007
Location: City of Light
Posts: 3943
Good Answers: 183
#22
In reply to #21

Re: Probability Question

04/13/2015 5:41 AM

The answer is not wrong but incomplete. It was a test and it worked perfectly.

Register to Reply
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 14331
Good Answers: 162
#24
In reply to #21

Re: Probability Question

04/13/2015 12:51 PM

for one thing, n was not specified as even or odd. if n is odd, then no amount of wrong throws will provide the correct answer. In other words, OP should stay single, or if he picks an even number of wives, he will need life insurance.

I really hope this fellow is not an acuary.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 14331
Good Answers: 162
#25

Re: Probability Question

04/13/2015 1:00 PM

since you define the present probability of getting n points from the previous two throws of the coin, what happened in the case it takes more than three tosses? Is this probability density general for all integer n, or only for even numbered n?

General case examination:

n=0, then P0=1/2(P-1-P-2), does not exist, rather Po=0. (previous throws do not exist), and also previous values do not exist???? also 2>n

n=1, then P1 = 1/2(Po-P-1), does not exist, P1=0, previous values and throws either do not exist, or have zero value. 2>n

n=2 P2=1 since no matter the outcome, he will get two points on the first throw.

n=3 P3=1/2 using the equation, since P2=1, and P1=0

etc etc ad nauseum.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru
Hobbies - Musician - New Member

Join Date: Feb 2012
Posts: 523
Good Answers: 17
#26

Re: Probability Question

04/13/2015 4:12 PM

"if Pn is the probability of getting exactly n points.

Pn=1/2 (Pn-1 - Pn-2)"

Pn is the probability of getting exactly n points. A probability is a number x such that 0≤x≤1.

Now, as someone who works with probability, this part confuses me: 1/2 (Pn-1 - Pn-2)

As written, I want to reduce what is in the parentheses (Pn-1 - Pn-2) = (-3). Then I am not sure if the equation has reduced to Pn = 1/(2*-3) or Pn = 0.5 * -3. In either case, Pn is a negative number, so it is not a probability.

Please restate the problem using standard notation. It may help to provide a link to the book it came from.

Register to Reply
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 14331
Good Answers: 162
#28
In reply to #26

Re: Probability Question

04/14/2015 1:16 PM

The problem is not one of algebra but it is one of notation. I don't particularly like the formulism, as the OP's formula is not inclusive as a recursion probability that starts with the 0th or the first iteration, but starts at (n-2)th iteration. I thing the whole thing is rubbish.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply Score 1 for Good Answer
Guru

Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 4496
Good Answers: 137
#29
In reply to #28

Re: Probability Question

04/14/2015 2:44 PM

Maybe I'm being dim, but I still don't understand the OP's question, and tend to agree with your last sentence. Perhaps you or somebody could rephrase it?

__________________
Give masochists a fair crack of the whip
Register to Reply
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 14331
Good Answers: 162
#30
In reply to #29

Re: Probability Question

04/14/2015 3:03 PM

I think the equation is unlikely to fit the situation he is referring to. It cannot work if n is odd since thrower gets 2 points for every tails, and n points for every heads, and the target is n. It appears that points accumulate until n is reached. If n = 0 , there is 50% chance on first throw, and 0% chance on succeeding throws. If n=1, the situation is exactly the same. If n=2, there is 100% probability of success with the first throw, since 2 pts awarded either outcome. if n=3, then 50% on first throw, 0% on all succeeding throws. Once again, and so on ad nauseum.

The whole thing is just silly rubbish.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru

Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 4496
Good Answers: 137
#36
In reply to #30

Re: Probability Question

04/20/2015 2:03 PM

OK I'm still puzzled, that's my problem, but thanks for trying!

__________________
Give masochists a fair crack of the whip
Register to Reply
Guru
Hobbies - Musician - New Member

Join Date: Feb 2012
Posts: 523
Good Answers: 17
#31
In reply to #28

Re: Probability Question

04/14/2015 3:11 PM

I agree that notation is the problem. As written, my mind will not go in Probability directions. (all those classes in probability and statistics petrified my mind?) I suspect the desired equation is more like Pn = ½(Pn-1 - Pn-2). Or, in English, when is the probability of n equal to one half the difference of the probabilities of n-1 and n-2?

Is that what the OP's question described? I'll have to go back to the beginning and look.

Register to Reply
Guru
Hobbies - Musician - New Member

Join Date: Feb 2012
Posts: 523
Good Answers: 17
#32
In reply to #31

Re: Probability Question

04/14/2015 3:35 PM

That can't be the correct interpretation, either. Pn < Pn-1 < Pn-2. That is, it is less likely to get n=3 heads than n-1=2 heads, and less likely to get n-1=2heads than n-2=1 head. So, since Pn-1 < Pn-2, the difference (Pn-1 - Pn-2) is always negative, so it can not define a probability.

Register to Reply
Guru

Join Date: Oct 2014
Location: Hemet, Land of milk and honey.
Posts: 2365
Good Answers: 36
#27

Re: Probability Question

04/13/2015 6:24 PM

I believe that math can be applied to this equation. Although there are a few variables that I can think of that can affect the results: How high does the coin go before it loses momentum and drops to the ground? How high is the coin flippers thumb from the ground when the coin is first flipped ? How many flip revolutions does the coin make ? Does the coin flipper flip the coin easier or harder when the coin flipper start flipping the coin? Is there a learning curve where the coin flipper learns how to make the coin land on heads or tails more than one side or less ?

Register to Reply
Guru

Join Date: Apr 2010
Location: About 4000 miles from the center of the earth (+/-100 mi)
Posts: 9910
Good Answers: 1141
#33

Re: Probability Question

04/19/2015 12:48 PM

Here's my suggestion:

It should be a simple computer program to write in your favorite language. Loop it, say 100 times, and see what comes up. Run it multiple times to see if you get the same answer. If you get a consistent result, at least you will know what the right answer is and then you can work out why.

Register to Reply Score 1 for Good Answer
Guru
Popular Science - Weaponology - New Member Engineering Fields - Engineering Physics - New Member Engineering Fields - Nuclear Engineering - New Member

Join Date: Dec 2007
Location: No. VA, USA (No, it does NOTu mean "won't go"!)
Posts: 1796
Good Answers: 75
#34
In reply to #33

Re: Probability Question

04/19/2015 5:08 PM

GA from me. But, if he can even DO this, it was the proverbial "stupid question" in the first place.

Reminds me of the time I came home from my Calculus course, and wrote a Basic (yeah, THAT language!) program to accept all the variables in my homework by text prompt, then figure out what I needed to know from what I didn't provide, and provide me the answer. My wife, who isn't a computer user/geek/nerd/dork asked me how I was going to learn Calculus if I made the computer do all the work. I assure her that if I could write a program to do it for me, I first had to know how to do it myself.

Near perfect score on the finals, so I must have been right. At least that time.

__________________
Been away a while. Miss all my old friends. Some of you I KNOW are still around. Where are the rest?
Register to Reply
Guru

Join Date: Mar 2007
Location: City of Light
Posts: 3943
Good Answers: 183
#35
In reply to #33

Re: Probability Question

04/20/2015 4:51 AM

100 times could be not sufficient and by the way how do you simulate the "fate" ? With a number generator of excel for instance ? It is a pseudo stochastic generator so that results are only partly valid.

Register to Reply Score 1 for Good Answer
Register to Reply 36 comments

Good Answers:

These comments received enough positive votes to make them "good answers".

"Almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, vote them!
Copy to Clipboard

Users who posted comments:

Anonymous Poster (1); Codemaster (3); Crabtree (1); Fredski (1); Haris (2); IdeaSmith (2); ignator (2); James Stewart (5); lyn (4); micahd02 (2); nick name (4); reward54 (3); Rixter (1); SolarEagle (1); StandardsGuy (1); Tom_Consulting (1); tonyhemet (1); Tornado (1)

Previous in Forum: Software to Solve Problem of Planning and Inventory Control   Next in Forum: What Happens if Earth Stops Rotating?

Advertisement