Yes but had you chosen the other card to begin with, those odds would be the same, therefore equal probability
50/50/90 rule - do I hear people snicker?
- Thread starter 123enen
- Start date
Yes but had you chosen the other card to begin with, those odds would be the same, therefore equal probability
WaySolid
Learner
- Joined
- 10 July 2004
- Posts
- 222
- Reactions
- 0
When you can use that to make money from forecasting visit the casino.
- Joined
- 5 June 2006
- Posts
- 533
- Reactions
- 1
Deal or no deal makes high or low offers to make the show interesting. No forumula.
The question contestants should ask themselves are "is the offer better than the odds I could get at the casino" ... if it is take offer everytime.
You can take the money to the casino down the track.
IE 2 cases 1c and 200k ... offer 150k ... TAKE IT ... then take it to the casino and bet it all on black for a better potential return. Or bet 100k on black and pocket the 50k.
:
But the rule in this thread is embarrasing .... the odds when you picked from 4 are no longer relevant in a 50 50 pick
The question contestants should ask themselves are "is the offer better than the odds I could get at the casino" ... if it is take offer everytime.
You can take the money to the casino down the track.
IE 2 cases 1c and 200k ... offer 150k ... TAKE IT ... then take it to the casino and bet it all on black for a better potential return. Or bet 100k on black and pocket the 50k.
:But the rule in this thread is embarrasing .... the odds when you picked from 4 are no longer relevant in a 50 50 pick
theasxgorilla
Problem solved... next bubble.
- Joined
- 7 December 2006
- Posts
- 2,343
- Reactions
- 1
Exactly to all of the above.
Both cards have a 50% chance of being the ace when the there are 2 remaining but the process leading to the selection of the cards is important.
If you switch cards the only way you can lose is if you chose the ace as your card.
If you chose any of the other cards you will end up with the ace when you switch.
This is why the odds when there are 4 cards are relevent. And the more cards there are the more likely you will not chose the ace and therefore end up with it when you switch.
If you switch cards the only way you can lose is if you chose the ace as your card.
If you chose any of the other cards you will end up with the ace when you switch.
This is why the odds when there are 4 cards are relevent. And the more cards there are the more likely you will not chose the ace and therefore end up with it when you switch.
- Joined
- 28 May 2006
- Posts
- 9,985
- Reactions
- 2
I sorta agree pepperoni
but not sure they offer high offers - or that they'd offer you 150K
heck if they did you'd have to take it.. like you say. And you could do what you like with the profit lol.
But the crime (to my mind) would be if they offered you $80K - when the fair amount was $100K - and you took it - only for you then to go to the local club say 8000 times before you die, spending $10 each time - and it ending up as $50K or so - when you had an excellent chance of turning it into $100K on "one turn of pitch and toss" or "one turn of the deal-or-no-deal challenge" etc. (imo)
WaySolid
Learner
- Joined
- 10 July 2004
- Posts
- 222
- Reactions
- 0
I think you will find that switching is the way to go!
The thing is that the probability does actually change.
There's quite a bit on the web about the three door game.
http://www.theproblemsite.com/games/monty_hall_game.asp
- Joined
- 5 March 2008
- Posts
- 951
- Reactions
- 141
Hi,
I can't believe this thread has gone on for so long.
In a 'fair' game you switch every time, because the odds are in your favour to do so.
If 10 cards are placed face down, and you chose 1 of them, you have a 10% probability of guessing which one is the ace.
The other 9 cards represent a 90% probability of the ace being there.
If the other person, in charge of the game knows where the ace is, and turns up 8 non ace cards, then the odds are still 90% that their last card is the ace, and your odds are still 10% of having the ace.
The odds never changed in that scenario.
If you think this is wrong, then I would really like to play some card games with you.
brty
I can't believe this thread has gone on for so long.
In a 'fair' game you switch every time, because the odds are in your favour to do so.
If 10 cards are placed face down, and you chose 1 of them, you have a 10% probability of guessing which one is the ace.
The other 9 cards represent a 90% probability of the ace being there.
If the other person, in charge of the game knows where the ace is, and turns up 8 non ace cards, then the odds are still 90% that their last card is the ace, and your odds are still 10% of having the ace.
The odds never changed in that scenario.
If you think this is wrong, then I would really like to play some card games with you.
brty
- Joined
- 5 June 2006
- Posts
- 533
- Reactions
- 1
Is this element in the original ... there is a big diff between this and random flips by a dealer IMO.
If the dealer knows the cards he will just flip the bs cards so 2 or 2000000 cards it was always gonna come to 50 50
- Joined
- 5 June 2006
- Posts
- 533
- Reactions
- 1
I see someone else clarified ... this makes it misleading bs ... better to say "you can pick this one card or these 3"!
.
- Joined
- 5 March 2008
- Posts
- 951
- Reactions
- 141
Pepper,
It does not come to 50/50.
If the odds started at 90/10, then that is what they remain, whether you see 'most' of the cards face up or face down makes no difference, the cards as delt are the same.
In the games mentioned, the dealer knows where the ace is, therefore all he is showing face up are the irrelevant cards. He has to have at least 8 irrelevant ones. If he shows them to you face up or face down makes no difference to the odds, he had a 90% probability of having the ace you had a 10% probability of having the ace.
Are you, per chance, interested in a game of cards???:
brty
It does not come to 50/50.
If the odds started at 90/10, then that is what they remain, whether you see 'most' of the cards face up or face down makes no difference, the cards as delt are the same.
In the games mentioned, the dealer knows where the ace is, therefore all he is showing face up are the irrelevant cards. He has to have at least 8 irrelevant ones. If he shows them to you face up or face down makes no difference to the odds, he had a 90% probability of having the ace you had a 10% probability of having the ace.
Are you, per chance, interested in a game of cards???
:brty
- Joined
- 28 May 2006
- Posts
- 9,985
- Reactions
- 2
I must be misunderstanding you brty. (or you're having a lend surely?)
There are two cards (at the end) - one is the ace , one isn't
and you say that there 's 90% chance one is, and 10% the other?
So when you play cards, if we could increase our bets at that point, you'd give me 9-1 if I added to my bet on my card?
..........
PS Rethink - Strange rules - Since when does the dealer know where all the cards are , and which ones to show you? - Are you saying all the cards are effectively face up for him (after being dealt), and face down for you? - and he chooses which ones to show you ?
I guess with enough rules like that you are right .
- Joined
- 28 May 2006
- Posts
- 9,985
- Reactions
- 2
On second thoughts, you might have talked me round to this philosophy korrupt lol. i.e. take the $80K (at least in my present predicament).
like trading - it depends whether you're talking about money you can spare, or money you need to stay afloat
https://www.aussiestockforums.com/forums/search.php?searchid=1456777
- Joined
- 28 May 2006
- Posts
- 9,985
- Reactions
- 2
The maths said go for the motsa
but the dice came down the wrong way
now I've got this bill - in fact lotsa
and no money to mathematically pay
but the dice came down the wrong way
now I've got this bill - in fact lotsa
and no money to mathematically pay
- Joined
- 5 June 2006
- Posts
- 533
- Reactions
- 1
Pepper,
It does not come to 50/50.
If the odds started at 90/10, then that is what they remain, whether you see 'most' of the cards face up or face down makes no difference, the cards as delt are the same.
In the games mentioned, the dealer knows where the ace is, therefore all he is showing face up are the irrelevant cards. He has to have at least 8 irrelevant ones. If he shows them to you face up or face down makes no difference to the odds, he had a 90% probability of having the ace you had a 10% probability of having the ace.
Are you, per chance, interested in a game of cards???
brty
I know but as I said as he knows where the cards are its all a charade.
He should ask "find the ace .... do you want to pick one card or 9 cards"
If he doesnt know where the cards are, as per the original post, there is no point in changing as they are all 1 in 4.
- Joined
- 28 May 2006
- Posts
- 9,985
- Reactions
- 2
Good point pepperoni - we need to define the game..
I'll repost the definition of the 50/50/75 rule:-
ok , I think I 've worked it out.
a) If the "moderator" originally knew where the ace was, and has a good memory, and is the one choosing which cards to turn over - you should change your choice (the odds are 75/25)
b) If the "moderator" originally knew where the ace was, and has a bad memory, and is the one choosing which cards to turn over , you might as well change your choice (as it's somewhere between 50/50 and 75/25)
c) If the "moderator" never knew where the ace was, and was above cheating or dealing from the bottom of the pack etc. - and is the one choosing which cards to turn over - You might as well change your choice just in case your assumption that he wasn't dealing from the bottom of the pack was wrong, lol.
d) If YOU were the one choosing which cards, it's 50/50. (irrespective of whether the moderator knew where the ace was or not).
Summary. You might as well change your bet when it gets down to 2 cards - nothing to lose. (imo).
I'll repost the definition of the 50/50/75 rule:-
ok , I think I 've worked it out.
a) If the "moderator" originally knew where the ace was, and has a good memory
, and is the one choosing which cards to turn over - you should change your choice (the odds are 75/25)b) If the "moderator" originally knew where the ace was, and has a bad memory, and is the one choosing which cards to turn over , you might as well change your choice (as it's somewhere between 50/50 and 75/25)
c) If the "moderator" never knew where the ace was, and was above cheating or dealing from the bottom of the pack etc. - and is the one choosing which cards to turn over - You might as well change your choice just in case your assumption that he wasn't dealing from the bottom of the pack was wrong, lol.
d) If YOU were the one choosing which cards, it's 50/50. (irrespective of whether the moderator knew where the ace was or not).
Summary. You might as well change your bet when it gets down to 2 cards - nothing to lose. (imo)
.
- Joined
- 31 May 2006
- Posts
- 1,941
- Reactions
- 2
If the moderator does know where the ace is then you should change because its 75/25 in favour of it being the one the mod has left.
If the moderator doesn't know, and is randomly turning cards over - then if the cards were in his lot there is a 2/3 chance he won't turn it over first go, a 1/2 chance he won't turn it over second go. Therefore if the card is in his lot of three and he hasn't turned it over through random selection then there is only a 1 in 3 chance he wouldn't have turned it over. So that makes me think the odds are in favour of not swapping because if it was the moderators lot of three there's a 2/3 chance he would have turned it over already.
i.e. extrapolate this out to a million - if the ace was in the moderators set of 999,999 cards and he is truning them over randomly, then odds on the moderator turning over 999999 cards without turning over the ace is very slim - thus if he manages to do this its likely to be because the ace is your card and not amongst his cards.
I could probably have explained that better but am feeling too lazy to rewrite it.
If the moderator doesn't know, and is randomly turning cards over - then if the cards were in his lot there is a 2/3 chance he won't turn it over first go, a 1/2 chance he won't turn it over second go. Therefore if the card is in his lot of three and he hasn't turned it over through random selection then there is only a 1 in 3 chance he wouldn't have turned it over. So that makes me think the odds are in favour of not swapping because if it was the moderators lot of three there's a 2/3 chance he would have turned it over already.
i.e. extrapolate this out to a million - if the ace was in the moderators set of 999,999 cards and he is truning them over randomly, then odds on the moderator turning over 999999 cards without turning over the ace is very slim - thus if he manages to do this its likely to be because the ace is your card and not amongst his cards.
I could probably have explained that better but am feeling too lazy to rewrite it.
- Joined
- 5 June 2006
- Posts
- 533
- Reactions
- 1
If the moderator does know where the ace is then you should change because its 75/25 in favour of it being the one the mod has left.
If the moderator doesn't know, and is randomly turning cards over - then if the cards were in his lot there is a 2/3 chance he won't turn it over first go, a 1/2 chance he won't turn it over second go. Therefore if the card is in his lot of three and he hasn't turned it over through random selection then there is only a 1 in 3 chance he wouldn't have turned it over. So that makes me think the odds are in favour of not swapping because if it was the moderators lot of three there's a 2/3 chance he would have turned it over already.
i.e. extrapolate this out to a million - if the ace was in the moderators set of 999,999 cards and he is truning them over randomly, then odds on the moderator turning over 999999 cards without turning over the ace is very slim - thus if he manages to do this its likely to be because the ace is your card and not amongst his cards.
I could probably have explained that better but am feeling too lazy to rewrite it.
I struggle with this ... they were all 1/4 when they started and 50/50 on last pick.
But yes nothing lose by changing cards.
The other one is obvious ... just a roundabout way of saying "which is more likely, the ace is *that* card, or one of the other 3!
- Joined
- 28 May 2006
- Posts
- 9,985
- Reactions
- 2
i.e. extrapolate this out to a million - if the ace was in the moderators set of 999,999 cards and he is truning them over randomly, then odds on the moderator turning over 999999 cards without turning over the ace is very slim - thus if he manages to do this its likely to be because the ace is your card and not amongst his cards.
I could probably have explained that better but am feeling too lazy to rewrite it.
lol
I struggle with this as well.
you're making it real complicated there cuttlefish - got my eyebrows in a knot here lol
It could also be argued (erroniously / mischievously) that there are two cards left (of the 1,000,000) - the one you chose when you had odds of 1 in 1,000,000 of getting it right, ...
and the one the moderator chose when he dismissed all the others - and when he had 1 in 999,999 chance of picking it if you missed it. Therefore the one he chose has the slightly better odds of being right
(PS you could drive a truck through that logic but after a couple of beers it starts to make more sense lol)probably exhausted this one surely
If you disagree with the OP's theory then you are quite ignorant.
The maths behind it is simple and it involves the player playing from the VERY BEGINNING. Now you are playing from the beginning you have picked one card and randomly (I mean of course if the dealer knows the ace then the game has absolutely no meaning to it) comes down to the last 2 of 10 cards, then that makes switching the card for you a 90% favourite from the beginning, of course the luck on the way is now disregarded simply because of the fact that you are now on the last 2 cards and you have played all the way through.
It is like the simple maths of if you have 2 different pairs of socks in the drawer, what is the chance of picking out a pair simultaneously - well 25%, however if you pick out one sock first then what are the odds? well it changes to 33% doesn't it?
Roulette too, the chances of you starting from spin number 1 and spinning 20 blacks in a row (the highest I have seen at the casino is 9 spins in a row - I won $200 from my original $5) is almost impossible, however if it happens and then you start playing from the spin thereafter then yes your chances are 50/50 of black coming up next spin.
It doesn't matter what game you play - maths is maths think what you like but our world revolves around these magic figures and formulas - it is the reason we are so technology advanced to date.
The maths behind it is simple and it involves the player playing from the VERY BEGINNING. Now you are playing from the beginning you have picked one card and randomly (I mean of course if the dealer knows the ace then the game has absolutely no meaning to it) comes down to the last 2 of 10 cards, then that makes switching the card for you a 90% favourite from the beginning, of course the luck on the way is now disregarded simply because of the fact that you are now on the last 2 cards and you have played all the way through.
It is like the simple maths of if you have 2 different pairs of socks in the drawer, what is the chance of picking out a pair simultaneously - well 25%, however if you pick out one sock first then what are the odds? well it changes to 33% doesn't it?
Roulette too, the chances of you starting from spin number 1 and spinning 20 blacks in a row (the highest I have seen at the casino is 9 spins in a row - I won $200 from my original $5
) is almost impossible, however if it happens and then you start playing from the spin thereafter then yes your chances are 50/50 of black coming up next spin. It doesn't matter what game you play - maths is maths think what you like but our world revolves around these magic figures and formulas - it is the reason we are so technology advanced to date.
