unforum
a.r.g.b.b

Welcome!
 New users, PLEASE read these forum guidelines. New posters, SEARCH before posting and read these rules before posting your killer new campaign. New players may also wish to peruse the ARG Player Tutorial.All users must abide by the Terms of Service.

You?

Why do we need your help?
Announcements
 Got a jones for some uF swag? Visit Ye Olde Tradin' Post!

 The time now is Fri May 24, 2013 6:47 am All times are UTC - 6 View posts in this forum since last visit View unanswered posts in this forum Calendar
 Moderators: AnthraX101, bagsbee, BrianEnigma, cassandra, Giskard, lhall, Mikeyj, myf, poozle, RobMagus, xnbomb
 Page 2 of 2 [27 Posts] Goto page: Previous 1, 2
Author Message
Fuseunderground
Decorated

Joined: 17 Dec 2005
Posts: 151

 forensick wrote: I think the biggest problem with this question is that it's

There is no problem with the question,

This card (like 'Illogical' and others) shows that the way people think about a problem,
is not necessarily the right way (In maths/logic/or whatever)
The correct answer for this puzzle reflects the situation in real life, honestly.
_________________
Like your hero TJ Hooker you tackle challenges head-on with determination and vigour paying scant attention to the law. This devil-may-care attitude may work for fictional crimefighters but it can be counterproductive in real life.

Posted: Fri Apr 28, 2006 1:23 pm
ringsting
Kilroy

Joined: 21 Jun 2006
Posts: 1

I think that where the card isn't clear is that it dosn't explain at what point in time the probability should be taken.

at point x in time, before any of the doors have been opened; the probability that A is correct is 1/3 and the probability that its not correct is 2/3. Hence when C is opened B becomes 2/3 as C=0 (according to the original calculation.)

however we move on in time and at point y in time, after C has been opened; we are simply left with a fresh choice of 2 doors, giving 50/50.

I think that you have to start each situation with a new calculation, otherwise you have to take into account all preceeding events such as: was the contestant chosen from a group of 100 people? if so you have the odds of 1/100 added onto the calculation ect

Posted: Wed Jun 21, 2006 6:38 pm
mama_needs_a_new_car
Boot

Joined: 15 Jun 2006
Posts: 33

Ringsting:

I absolutely agree - the frank fact is that we end the contest with two doors - and either a goat or a yacht behind each. 50/50. Two choices, two doors, two prizes - equal probability.

The other numbers (1/3, 2/3) are only in play within the context of the whole contest.

I will assume the host was always going to eliminate one of the three doors and leave the contestant with two choices - it is like forcing a card in a magic trick.

I will bow down to the mathmatic "authorities" and submit the answer they want (like taking a test in school with a lousey teacher who just wants you to regurgtate his/her own opinions), but I don't have to like it.

Posted: Thu Jun 22, 2006 12:00 am
oliverkeers13
Entrenched

Joined: 23 May 2005
Posts: 917
Location: London, UK

No, similar to the theory of evolution, in that way. No matter how much sense it makes, some people will insist on believing in creationism.
_________________
"You're talking last ditch, I need top drawer" V
"To be in opposition is not to be a nihilist" CH
"im iver an idiot or a genus" Dekuprince
Perplex City Video

Posted: Thu Jun 22, 2006 3:17 am
Ashin
Veteran

Joined: 22 Nov 2005
Posts: 140

Re: Ringsting:

 mama_needs_a_new_car wrote: I absolutely agree - the frank fact is that we end the contest with two doors - and either a goat or a yacht behind each. 50/50. Two choices, two doors, two prizes - equal probability. The other numbers (1/3, 2/3) are only in play within the context of the whole contest.

Hey dude. You're right that the probability of winning and and losing is equal (50/50). That's not what the question is asking, the question is "What is your probability of winning if you switch?"

The 50% winning field gets split into thirds, 2 of which are switching, and 1 of which is not-switching.

Start liking it.

Posted: Thu Jun 29, 2006 4:24 pm
GreenWindmill
Decorated

Joined: 21 Apr 2006
Posts: 195
Location: Midlands, UK

Look at it this way:

Let's assume the yacht is behind door 3 each time.

The gameshow host is always going to leave the door you pick and one other (which will be door 3 if you haven't picked it, and for argument's sake, door 1 if you did pick 3).

There are therefore 3 possible scenarios:

You pick door 1: The host eliminates door 2, you're left with 1 & 3. If you switch you win the yacht.

You pick door 2: The host eliminates door 1, you're left with 2 & 3. If you switch you win the yacht.

You pick door 3: The host eliminates door 1, you're left with 2 & 3. If you don't switch you win the yacht.

You win the yacht by switching in 2 of the 3 scenarios. In other words there's a 2/3 chance of winning if you switch and 1/3 if you don't.

As people have stated previously, this is more obvious with more doors - consider it with 100.

Not that this post is any real use, the correct answer has been confirmed looong ago, just trying to convert some non-believers!

Posted: Wed Jul 05, 2006 6:02 am
Factor41
Guest

Aaaahhhh

 GreenWindmill wrote: Not that this post is any real use...

No, no, it was useful. It's all in the wording. It is the probability that you will get the prize if you switch, not the probability that you will pick the correct one of two doors. Makes more sense if you say it like that, and with those scenarios spelt out.

Thanks.

Posted: Mon Sep 18, 2006 4:53 pm
GreenWindmill
Decorated

Joined: 21 Apr 2006
Posts: 195
Location: Midlands, UK

 Quote: No, no, it was useful.

Woo hoo! A useful post from the Windmill - that's a definite first!
_________________
Mmm... Sacrilicious.

Posted: Tue Sep 19, 2006 4:48 am
X9Tim
Boot

Joined: 29 Sep 2006
Posts: 16

 GreenWindmill wrote: Look at it this way: There are therefore 3 possible scenarios: You pick door 1: The host eliminates door 2, you're left with 1 & 3. If you switch you win the yacht. You pick door 2: The host eliminates door 1, you're left with 2 & 3. If you switch you win the yacht. You pick door 3: The host eliminates door 1, you're left with 2 & 3. If you don't switch you win the yacht.

You pick door 3: The host eliminates door 2, you're left with 1 & 3. If you don't switch you win the yacht.

Then there are 4 scenarios and you win in 2 of them whether you switch or not.

I've read this type of problem and its explanation once or twice before, and I'm still not sure it's really right....

I DID post 1/2, 1/2 first time without being sure, but I knew what the other "correct" solution was....
Still I've got the points and thats what counts

Posted: Fri Sep 29, 2006 10:49 am
FairmontKing
Boot

Joined: 04 Sep 2006
Posts: 25
Location: Michigan, USA

I studied this problem as an example in a graduate-level decision analysis class. I, too, struggled with the given solution at first. The reason the answer is not as straightforward as it should be is because we really don't know Jaunty's intentions and motives.

For the given answer to be correct, the following assumptions must be true:

1. Jaunty knows which door the prize is behind.
2. Jaunty decided ahead of time that regardless of which door you chose, he was going to show you a door without the prize.

Basically, our odds only improve if we switch because Jaunty is trying to help us.

Posted: Sat Sep 30, 2006 6:55 pm
hobyrne
Guest

Precisely what FairmontKing says. It depends on Jaunty's motivations and instructions. If the director of the show tells him, "You *must* open a goat door", that is one scenario. However, in the eerily coincidental [/sarcasm] parallel case of Monty Hall, Monty did _not_ *have* to open a door. It made for better TV, when he did, but he did not have to every time.

Therefore, if Monty was stupid, and wanted to save the network money, then every time someone chose a goat, he would end the game at that decision and the contestant is a loser, and every time someone chose the yacht, he would continue the game and give the contestant another chance to lose.

Of course, in this case, people would soon realise that the only time they are ever given a choice is when they have the winning door to begin with. So, what Monty really did, was to sometimes open a goat door when the contestant chose a goat. So, the best Monty could do to save the network money, is: If the contestant chooses the yacht, open a goat door. If the contestant chooses a goat, open the other goat door 1/2 of the time.

Conversely, if Monty wanted the contestants to win, he could end the game whenever someone chooses right, and give the contestant another chance to win if he chose wrong.

The card does not say that Jaunty *had* to open a goat door, just that he _did_. For that reason, the probabilities are 0.5 and 0.5.

Posted: Tue Oct 03, 2006 8:20 am
hobyrne
Guest

Okay, since this _is_ a confusing issue, here is a worked-out example.

The three prizes are: Goat 1, Goat 2, Yacht. Making a distinction between the goats is important. If you flip two coins, there are three outcomes: two heads, one heads and one tails, two tails. If you flip a nickel and a dime, there are four outcomes: nickel heads & dime heads, nickel heads & dime tails, nikel tails & dime heads, nickel tails & dime tails.

Monty Hall has the following instructions: If the person chooses Goat 1, let him have it. If the persion chooses Goat 2, open the door with Goat 1. If the person chooses the yacht, open the door with Goat 1.

Chooses goat 1: Happens 1/3 of the time. Contestant loses.

Chooses goat 2: Happens 1/3 of the time. Contestant gets choice: wins if he switches.

Chooses yacht: Happens 1/3 of the time. Contestant gets choice: wins if he doesn't switch.

So, the contestant gets a choice 2/3 of the time. HALF of those times he gets a choice, he should switch, HALF of the times he gets a choice, he shouldn't switch.

BTW: Interesting end note. If the contestants switch half the time, the overall chance of winning the prize is 1/3... exactly the same as if this little game were done away with and he just always got his first choice. The extra game is just for show, to make it *seem* more exciting for TV.

Posted: Tue Oct 03, 2006 8:37 am
Display posts from previous:   Sort by:
 Page 2 of 2 [27 Posts] Goto page: Previous 1, 2

You can post new topics in this forum
You can reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum