A Maths question.

[JustOneUK]

Originally posted by moneyman
do this with a hundred boxes with the presenter opening 98 empties you will get the right box once but the wrong box every other time. so swap

(let's just replace 100 for 22 in your example)

not Originally posted by moneyman
do this with twenty two boxes with the presenter opening 20 empties you will get the right box once but the wrong box every other time. so swap

so you agree?
if you get to the last two boxes in deal or no deal and the prize is still there you should swap?

In order to get to the last 2 boxes in deal or no deal the options are the same as in the Monty hall paradox, so by definition the result must be the same? swap your box.

Where the prize = 1:
door 1 open door 2 and you swap. you get 3 (lose)
door 1 open door 3 and you swap. you get 2 (lose)
door 2 open door 1 and you swap. you get 3 (void) cannot do that
door 2 open door 3 and you swap. you get 1 (Win)
door 3 open door 1 and you swap. you get 2 (void) cannot do that
door 3 open door 2 and you swap. you get 1 (win)

have 1 open box 2 and you swap. you get 3 (lose)
have 1 open box 3 and you swap. you get 2 (lose)
have 2 open box 1 and you swap. you get 3 (void) prize has gone
have 2 open box 3 and you swap. you get 1 (Win)
have 3 open box 1 and you swap. you get 2 (void) prize has gone
have 3 open box 2 and you swap. you get 1 (win)

James.

[JustOneUK]

Woohoo, let's forget everything I posted in this thread, wires seem to have been crossed along the way and I can see that I am right.

Moneyman, no need for a reply to my last post.

James.

[Jiminite]

Originally posted by AGB
The two events are not dependant on one another and hence their probability is measured seperatly, regardless of what the presenter knows (but assuming he doesn't force your choice).

In the first event, the chance is 1 in 3 (33/33/33)of getting the correct box. The second event is a 1 in 2 chance (50/50) as one box has the money, the other is empty, and you are the one choosing (assuming you are indepenadnt).

It's the same as picking one coloured ball from a bag that contains two red and one blue. The chance of picking a blue is 1/3, red is 2/3. If one red is removed, the chance of picking the blue is 1/2 and red is 1/2.

You have to remember to 'reset' the probability after an empty box has been opened.

It doesn't matter what you do, but a 50/50 chance is fialy good!

Yeah, I totally agree with this. To start with there's a one in three chance of your box having the million. It's ONE because there's the money in ONE of the boxes. It's THREE because there are THREE boxes in play. When the presenter opens a box to reveal that it's empty, he's taking it out of the game. That opened box has now a zero chance of containing the money. There's now a ONE (because there's still one box containing the million) in TWO (because there are TWO boxes in play).

Taking the Deal Or No Deal example. There's a 1 in 22 chance of them having £250,000 to start with because there's only 1 £250,000 in 22 possible boxes. Five boxes are open, but let's say none of them contained £250,000. There's zero chance of the £250,000 being there because they were revealed to have different amounts in, so therefore they have been taken out of the game and 17 remain. There's now a 1 (there's still 1 £250,000) in 17 because 17 boxes remain with the possibility of having the £250,000 in it. When it get's down to the final two (and let's say it's either 1p or £250,000). There's no chance that the 1p or £250,000 being in the other boxes, so there's only two possible boxes that could contain those amounts. There's a 1 (there's still 1 £250,000) in 2 (2 possible boxes) of a selected box containing the £250,000. It's 50/50 chance, so it doesn't matter if you swap at the end or not.

[nick.martin]

Originally posted by Jiminite
Yeah, I totally agree with this. To start with there's a one in three chance of your box having the million. It's ONE because there's the money in ONE of the boxes. It's THREE because there are THREE boxes in play. When the presenter opens a box to reveal that it's empty, he's taking it out of the game. That opened box has now a zero chance of containing the money. There's now a ONE (because there's still one box containing the million) in TWO (because there are TWO boxes in play).

Taking the Deal Or No Deal example. There's a 1 in 22 chance of them having £250,000 to start with because there's only 1 £250,000 in 22 possible boxes. Five boxes are open, but let's say none of them contained £250,000. There's zero chance of the £250,000 being there because they were revealed to have different amounts in, so therefore they have been taken out of the game and 17 remain. There's now a 1 (there's still 1 £250,000) in 17 because 17 boxes remain with the possibility of having the £250,000 in it. When it get's down to the final two (and let's say it's either 1p or £250,000). There's no chance that the 1p or £250,000 being in the other boxes, so there's only two possible boxes that could contain those amounts. There's a 1 (there's still 1 £250,000) in 2 (2 possible boxes) of a selected box containing the £250,000. It's 50/50 chance, so it doesn't matter if you swap at the end or not.

Try turning it around, you get to open 2 boxes and you know that one will be empty because obviously it has to be, would you pick the 2 boxes or the 1 box?

[big_phoenix]

Don't forget there these are not yes and no choices. Money or no Money.

You might be luck and havy the £250k and the £125k left then who cares!

[moneyman]

the deal or no deal is much more complicated and more game theory because it depends what outcome you need rather than win or lose. so taking £20,000 when you have a 50/50 chance of winning £250,000 may not be too stupid for that player if he cant afford to lose.

the stupidest contestant i have ever seen was on who wants to be a millionaire. she refused to guess when she was on £1000 and had taken a 50/50. 0 chance of losing 50% chance of improving and she took the money. poor chris just couldnt convince her. aghhhhh. muppet.