SRL Archive - News and General

Imagine that you are at a strange game show where you are presented with 3 doors. The host informs you that behind one of the doors is $1,000,000 (tax free). and behind the other two doors is a bar of soup and bucket. You are asked to pick one of the doors.

With much trepidation, you decide on a door. A hush comes over the crowd (that suddenly appeared out of nowhere) The host looks at you and says "Ok, im going to open one door that doesn't have the $1,000,000 behind it." So with much bravado, he opens a door to reveal the bar of soup.

He then gives you this ultimatum "You can keep your door or you can switch. Which will you do?"

So, which do you do? Stick, or switch? And why?

Yes, you switch. It was explained in the movie 21, but I CBF to look up the explanation. To make this post short, you get 66.666% if you change, 33.333% if you don't.

From: Sandstorm
Yes, you switch. It was explained in the movie 21, but I CBF to look up the explanation. To make this post short, you get 66.666% if you change, 33.333% if you don't.

How sure are you of that answer? After all, movie logic isn't necessarily RL logic.

From: boberman
How sure are you of that answer? After all, movie logic isn't necessarily RL logic.

Because it sounded smart in the movie(Lol :P). And because I believe I've seen it explained multiple times from different sources.

It is to your advantage to switch. The logic presented in the movie 21 is the actual logic behind this problem.

Edit: It's called the Monty Hall problem. It ends up with switching winning 2/3s of the time.

Switch we did it @ school.

Switching is the best option. There's one of three choices.

1. You pick the winner. Switching is a loss.
2. You pick Loss 1. Switch = win.
3. You pick loss 2. Switch = win.

In two out of three situations switching will help you win.

I would say switch, but voted it doesn't really matter becouse the poll where on startpage so just had to vote to see the thread, or i had to find it :p

~D-M

Gah, I hate you all :P

I never saw 21 or this problem before the class where we discussed it. So of course I was like "Oh, you have a 50/50 chance of being right so it doesn't matter".

I was hoping more of you hadn't seen the problem before so we could have a discussion about it, guess not. :P

I'd say not to switch, go with your instinct!

From: richk1693
Switching is the best option. There's one of three choices.

1. You pick the winner. Switching is a loss.
2. You pick Loss 1. Switch = win.
3. You pick loss 2. Switch = win.

In two out of three situations switching will help you win.

you forgot 2 situations-

You pick lose 1 and stick with it
you pick lose 2 and stick with it

From: Esteban
you forgot 2 situations-

You pick lose 1 and stick with it
you pick lose 2 and stick with it

There is no 'stick with it' if you always switch…

There are 6 possible outcomes. 2 groups of 3.

Group 1- stick
Pick winner- win
Pick loser1- lose
Pick loser2- lose

Group 2- switch
Pick winner- lose
Pick loser1- win
Pick loser2- win

As you can see, switching gives you 2/3 chance, sticking gives you 1/3.


If you want more of a discussion, here's one. There are 2 doors, one good, one bad. There are 2 guards, one always lies, and one always tells the truth. You go up to one of the guards, and ask them 1 question, to find out which is the good door. What is that question? Both guards know which door is which, but they are not standing next to a specific door. There is more than one question that will work.

From: Boreas

If you want more of a discussion, here's one. There are 2 doors, one good, one bad. There are 2 guards, one always lies, and one always tells the truth. You go up to one of the guards, and ask them 1 question, to find out which is the good door. What is that question? Both guards know which door is which, but they are not standing next to a specific door. There is more than one question that will work.

Ask one of them which door would the other guard say is the good door. Then pick the opposite of which he says.

From: senrath
Ask one of them which door would the other guard say is the good door. Then pick the opposite of which he says.

Correct! But don't say why until we get some more answers…

How about if the guards don't know each other?

From: senrath
Ask one of them which door would the other guard say is the good door. Then pick the opposite of which he says.

Aha, but that's the simple version of the answer.
What if I add this:
Both the guards do not know which of them lies, so then can't tell if the other guard lies or not. Aka the one who lies doesn't know he lies, and the one who speaks the truth doesn't know he speaks the truth.
Have fun. :p

EDIT: Read the post above my post, Boreas beat me to it. ;)