AndyC_772

iTrader: (2)

Anyone ever had curried goat? I hear it's nice...

Turbohot

Yes, but this thread isn't about the curry, Moira.

Suresh

Another variable in the puzzle believe it or not is your name. If you are called Robert Newman the chances are you would indeed swap but not choose the other closed door, but the open door with the goat.

http://www.bbc.co.uk/news/uk-england-wiltshire-24066227


I'm calling bollocks on this I'm afraid. Once the first door has been opened to reveal the goat, the probability of picking the car changes from 1:3 to 1:2. The key point is the wording. If you are asked to *choose again* and choose the same door then the probability is 1:2 and if you choose the other door it is also 1:2.

The key point is you have to choose again in order to change the quoted mathematical probability of your choice. It doesn't matter if you pick the same door or not and so in real life your chances of winning do not increase by picking the other door only mathematically so.

Leslie

They will eat anything-even your trousers if you let them!

Les

tarmac terror

iTrader: (2)

I'd take the goat - game shows always offer crap cars as prizes. Using this reverse psychology, i'd probably win the feckin car anyhow.

AndyC_772

iTrader: (2)

Can if you like, but Saxo Boy has already posted a perfectly correct explanation of the odds, and why swapping gives you a 2/3 chance of winning as opposed to 1/3.

The key thing to notice, which perhaps hasn't been stated in so many words, is that when you make your initial choice, you're influencing the door that the host has to open.

In 1/3 of cases, you randomly choose the car, and the host has a choice of either door to open and show you a goat. In these cases, of course, swapping means you win the other goat.

But, in 2/3 of cases, you choose one of the goats, and the host has no choice but to show you the location of the only other goat. You've forced his hand, and by picking the door he hasn't opened, you win the car.

Suresh

Whether you have a car or a goat the host will always take a goat out of play - whether you have the car or the other goat. This is a bit of showmanship and the probability changes when the host reveals the goat from 1/3 to 1/2 as there are only a car and a goat left in the game. i.e. The original 1/3 probability is no longer relevant as the population is reduced to 2.

So after one goat has been taken out, essentially you have two choices and they are equally probable i.e. 50/50.



It could be that I'm wrong of course, but the probability of that event is low...

cster

You are not only wrong, you are a bit obtuse.
The chances of the car being behind the other two doors is always 2/3 - fact.
The host opening up the door with the goat does not in any way change this fact. He is in effect just helping you to win the car - if you will let him.

ReallyReallyGoodMeat

As has been said, it's always easier when you take it to the extreme and imagine 1000 doors and the gameshow host removes 998 guaranteed goats, leaving two doors for you to choose from.

It is not 50/50 when there are only two doors remaining as there is a greater likelihood of a goat behind one door than the other. As the gameshot host removes doors from the equation, he is telling you the chance of a goat behind the remaining door increases, but tells you nothing about the door you chose (as he is not able to remove it from the equation).

c_maguire

So when there are 2 cars and 1 goat, and the host opens a door with a car behind it, can we assume that you now have a greater chance of winning the remaining car by sticking with your original choice?

I am inclined to agree with Suresh, in that being able to choose again makes this a new game with a 50/50 chance

hodgy0_2

And the other extreme is that the game show reveals a goat before you make your choice

Then it is 50/50

Lisawrx

iTrader: (1)

This won't go down well on here, sorry, but I'm happy that I don't care enough to bother trying to understand.

kenc

iTrader: (6)

When the game show host picks out a goat and you have a chance to change your mind on what you have already picked.....
If we take that as a start point for a new game in which you have now the choice of 2 doors... 1 with a car and 1 with a goat....
This to me is a 50/50 chance... The host had changed it from a 33.3% chance to a 50% chance....
Whether you change your mind or not does not effect your odds.. 2 doors and 1 car is always going to be 50/50 which ever door you pick.

f1_fan

iTrader: (9)

Completely and utterly wrong

I can understand anyone faced with the question initially thinking it will be 50/50, but after a whole article linked on this thread pointing out why it's not and then 3 or 4 illustrated examples as to why it's not and you still think it's 50/50. FFS!!!!!

f1_fan

iTrader: (9)

That doesn't surprise me

BoozyDave

iTrader: (8)

completely wrong

Bubba po

If anybody doubts the truth of this, I advise them to set up the game with a partner and run it about thirty times. Change whether you stick or swap every turn and tell us what you come up with.

I say again - this has been proved empirically, if you don't believe the mathematics.

AndyC_772

iTrader: (2)

When you make the initial choice it's a 1 in 3 chance that you've picked the car, and a 2 in 3 chance that you've picked a goat. Agreed?

If you've already picked the car with your initial choice then switching later on means you'll lose. So, there's a 1 in 3 chance that you'll lose if you switch. But...

If you've already picked a goat - a 2 in 3 chance, remember - then the host shows you the position of the other goat. Both goats are accounted for: your initial choice, and the one you've just been shown. This means that if you switch at this point, you will win the car. 2 in 3 chance.

c_maguire

I know, I've seen it and the explanation a long time ago, I just have this irrational urge to bait F1 and there are no gay threads running at the moment. The Winter tyres one will probably resurface soon though with a bit of luck.

f1_fan

iTrader: (9)

Ah the old 'I'm not f**king thick, I was only joking ploy'. Trouble is several other of your 'contributions' have removed any lingering doubt as to the truth about that

cster

Here is a question - does the host always offer a choice, or does he only offer it when he knows that there are two goats behind "his" two doors?
Or does he only make the offer half the time on a random basis?
OK, that is two questions.

Turbohot

No, that is 3 questions.

You ask:

1. Does the host always offer a choice?

or

2. Does he only offer it when he knows that there are two goats behind "his" two doors?

or

3. Does he only make the offer half the time on a random basis?


Now if you only asked 2 questions, then prove me wrong. Call it Cster puzzle.

Suresh

After reading the wikipedia page on this I see that a number of very bright people didn't buy it initially. So nay-sayers are in good company. The little green man argument is where I was coming from and this is indeed true but it seems not the full picture. So for the little green man who comes down to earth when only 2 doors are available it *is 50/50, but for our hapless game contestant it isn't. I guess I can live with being both right and wrong :nods:

P.S. I've had curried goat in Jamaica and it tasted like chicken. Or was it lamb?

zip106

Is Monty Hall the gardening bloke off the telly?