Page 1 of 3

1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 9:06 am
by wub
Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?"

Image

Is it to your advantage to switch your choice?



(Yes, this does work on the basic principle that you want to get the car instead of a goat)

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 9:08 am
by dickman69
The first pick is 1/3

The second pick is 1/2

Better chance in 2nd pick

Better switch

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 9:09 am
by Riddles
rayman612 wrote:The first pick is 1/3

The second pick is 1/2

Better chance in 2nd pick

Better switch
yup, pretty simple really

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 9:10 am
by garethom
Yeah.

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 9:55 am
by ascent
I don't know why I come here anymore may as well stay on bb.com :lol:

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 9:56 am
by wub
ascent wrote:I don't know why I come here anymore may as well stay on bb.com :lol:
:mrgreen:


You would be missed though!

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 10:16 am
by m8son666
yeah its best to switch, derren brown explains why in detail in one of his books but i don't remember

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 10:18 am
by Riddles
its also in 21. that film with kevin spacey

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 11:45 am
by test_recordings
I wouldn't because I'm a stubborn arse like that.

Everyone else says they would though it seems

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 12:10 pm
by Samuel_L_Damnson
I would rather have the goat tho :P

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 1:06 pm
by AxeD
Switching makes the chance on getting the car 2/3, not switching basically gives you
a 1 in 3 chance. When I approach it logically though, I say it doesn't matter :)

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 1:38 pm
by lovelydivot
No - It's been reduced to a 50/50 - doesn't matter.

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 1:40 pm
by wub
lovelydivot wrote:No - It's been reduced to a 50/50 - doesn't matter.
Has it?

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 1:41 pm
by Nihilism
wub wrote:
lovelydivot wrote:No - It's been reduced to a 50/50 - doesn't matter.
Has it?
There's a 50/50 chance that it did.

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 1:45 pm
by Riddles
Contestants who switch have a 2/3 chance of winning the car, while contestants who stick to their choice have only a 1/3 chance. One way to see this is to notice that, 2/3 of the time, the initial choice of the player is a door hiding a goat. When that is the case, the host is forced to open the other goat door, and the remaining closed door hides the car. "Switching" only fails to give the car when the player picks the "right" door (the door hiding the car) to begin with. But, of course, that will only happen 1/3 of the time.

from the wiki on the subject: http://en.wikipedia.org/wiki/Monty_Hall_problem

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 1:55 pm
by AxeD
That kind of spoils it, but yeah that's what I thought as well.

Wonder if it's actually the case when you do the experiment 100 times though.

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 2:02 pm
by ezza
pickled me :lol:

this guy explains it http://www.youtube.com/watch?v=3r6JR6Zw_Yk (spoiler lol)

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 2:33 pm
by mIrReN
no why would I? If I get a goat I can milk it + just download the car

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 2:34 pm
by wub
mIrReN wrote:no why would I? If I get a goat I can milk it + just download the car
Image

Re: 1000 math PhDs got this wrong - the Monty Hall problem

Posted: Wed Feb 19, 2014 3:11 pm
by lovelydivot
OH OK I get it...

Bu that's not based on math - That's based on educated assumption being the premise of the reveal.