~The BrAiN tEaSeR Thread~

[November Rain]

don't look other peeps but ahura, isn't that

Spoiler

2/3 instead of 1/2

 

[Ahura Mazda]

don't look other peeps but ahura, isn't that

Spoiler

2/3 instead of 1/2

Spoiler

Well he stated that we know what is behind one of the doors. there are 2 doors left. Therefore if the door is eliminated he has a 1/2 chance.

I assumed the door was gone was no longer part of the equation because it was a known entity.

 

[November Rain]

Spoiler

Well he stated that we know what is behind one of the doors. there are 2 doors left. Therefore if the door is eliminated he has a 1/2 chance.

I assumed the door was gone was no longer part of the equation because it was a known entity.

Spoiler

Aha, but when he made his decision, he had a 1 in 3 chance he picked the right one.

consider it being a consideration of win or other.

At the beginning he has a 1/3 chance of winning and a 2/3 chance in losing.

if he picks one box, he has a 1/3 chance of winning and the combined other two boxes have a 2/3 chance of winning

Since one door was opened 'after' he made his choice, it's 1/3 probability for the 'other' section has now been transferred to the unchosen box since the box chosen by the contestant still has a 1/3 chance of winning.

so the unchosen box is twice as likely to be the winning box than the originally chosen box.

hence the 2/3 instead of a 1/2 probability.

 

[Ahura Mazda]

Spoiler

Aha, but when he made his decision, he had a 1 in 3 chance he picked the right one.

consider it being a consideration of win or other.

At the beginning he has a 1/3 chance of winning and a 2/3 chance in losing.

if he picks one box, he has a 1/3 chance of winning and the combined other two boxes have a 2/3 chance of winning

Since one door was opened 'after' he made his choice, it's 1/3 probability for the 'other' section has now been transferred to the unchosen box since the box chosen by the contestant still has a 1/3 chance of winning.

so the unchosen box is twice as likely to be the winning box than the originally chosen box.

hence the 2/3 instead of a 1/2 probability.

Spoiler

I understand your reasoning and you are right in so far that door is part of the equation. However, taking it out because it is no longer a factor in your decision process would make it a 1/2 chance.

However, your calculations are correct and undeniable.

 

[wiegeabo]

Spoiler

I understand your reasoning and you are right in so far that door is part of the equation. However, taking it out because it is no longer a factor in your decision process would make it a 1/2 chance.

However, your calculations are correct and undeniable.

Spoiler

Think of it this way. Let's say there were 20 doors. You pick one. Every door except the one you picked and one other door is opened. Do you still think you have a 50-50 chance of being right? Or did you have a 1/20 chance of picking the right door, and now there's a 19/20 chance the single door they didn't open is the right one?

If they had opened one of the doors, then asked you to choose one, you would have had a 50-50 shot because there were two choices.

But, because you picked out of 3 doors, you only had a 1/3 chance. Them opening one of the doors doesn't change the fact that you only had a 1/3 chance of being right. Since probability always equals 1, there must be a 2/3 chance (1-1/3) the other door has the prize. So you should always switch.)

 

[DeaDheaD]

Spoiler

Think of it this way. Let's say there were 20 doors. You pick one. Every door except the one you picked and one other door is opened. Do you still think you have a 50-50 chance of being right? Or did you have a 1/20 chance of picking the right door, and now there's a 19/20 chance the single door they didn't open is the right one?

If they had opened one of the doors, then asked you to choose one, you would have had a 50-50 shot because there were two choices.

But, because you picked out of 3 doors, you only had a 1/3 chance. Them opening one of the doors doesn't change the fact that you only had a 1/3 chance of being right. Since probability always equals 1, there must be a 2/3 chance (1-1/3) the other door has the prize. So you should always switch.)

Spoiler

It started out with a 33% chance, but as more information was given you now have a 50% chance, because one door was eliminated from the game and the problem.

 

[Movies205]

Spoiler

Think of it this way. Let's say there were 20 doors. You pick one. Every door except the one you picked and one other door is opened. Do you still think you have a 50-50 chance of being right? Or did you have a 1/20 chance of picking the right door, and now there's a 19/20 chance the single door they didn't open is the right one?

If they had opened one of the doors, then asked you to choose one, you would have had a 50-50 shot because there were two choices.

But, because you picked out of 3 doors, you only had a 1/3 chance. Them opening one of the doors doesn't change the fact that you only had a 1/3 chance of being right. Since probability always equals 1, there must be a 2/3 chance (1-1/3) the other door has the prize. So you should always switch.)

Spoiler

I'm not a statistical student so perhaps this is what clouds my judgement but I thought of that, however my main problem with it is that it doesn't address the fact that you still might of chosen right in the first place... Then again I suppose the objective is to just up your probability.

 

[Ahura Mazda]

Spoiler

Think of it this way. Let's say there were 20 doors. You pick one. Every door except the one you picked and one other door is opened. Do you still think you have a 50-50 chance of being right? Or did you have a 1/20 chance of picking the right door, and now there's a 19/20 chance the single door they didn't open is the right one?

If they had opened one of the doors, then asked you to choose one, you would have had a 50-50 shot because there were two choices.

But, because you picked out of 3 doors, you only had a 1/3 chance. Them opening one of the doors doesn't change the fact that you only had a 1/3 chance of being right. Since probability always equals 1, there must be a 2/3 chance (1-1/3) the other door has the prize. So you should always switch.)

Spoiler

I was not arguing whether I should switch or not, given that is what I had stated initially. I was just stating that in my mind I discounted the door which I knew the resultn of making it 1/2. however, I did mention that the 2/3 was statistically correct.

 

[November Rain]

Spoiler

I'm not a statistical student so perhaps this is what clouds my judgement but I thought of that, however my main problem with it is that it doesn't address the fact that you still might of chosen right in the first place... Then again I suppose the objective is to just up your probability.

I think the stats don't represent the practicality of the problem.

not to mention what would realistically occur.

 

[Movies205]

I think the stats don't represent the practicality of the problem.

not to mention what would realistically occur.

Well now we're simply arguing from two different mind-sets, how that stastician doesn't care of the practicality, I would assume a statistician would always plan on a loss of sometype at the lowest possible percentage, however how he plays the game he is the safest.

The romantic who has no need for numbers plays the game based on luck which provides him the upshot of winning the most, it ups his probability of losing

So perhaps it more practical than we give it credit for

 

[wiegeabo]

Spoiler

It started out with a 33% chance, but as more information was given you now have a 50% chance, because one door was eliminated from the game and the problem.

Spoiler

The additional information has no bearing on the probability the chosen door is correct because it is given after the choice is made. There is only a 1/3 chance the correct door is chosen. One of the doors being opened doesn't change the fact that the door was chosen when all three were still closed.

Try this experiment at home with 3 playing cards: A, K, Q. Pick a card, then flip one of the others to open the door. (If you flip the Ace, start over because your not supposed to know where the prize is.) Only 1/3 of the time will the Ace be the card you picked. 2/3 of the time it will be the other card.

Or, another way to think about it. Let's say you always pick the left card. When you deal, 2/3 of the time the Ace will be in the middle, or on the right. The trick, if you can call it a trick, is that the game show knows which of those 2 cards has the Ace. So they always flip the other card, leaving the Ace and the chosen card. If the game show just randomly picked on of those two cards (doors) to show, 1/3 of the time they'd expose the money. So they don't randomly pick which on the show.

 

[November Rain]

Well now we're simply arguing from two different mind-sets, how that stastician doesn't care of the practicality, I would assume a statistician would always plan on a loss of sometype at the lowest possible percentage, however how he plays the game he is the safest.

The romantic who has no need for numbers plays the game based on luck which provides him the upshot of winning the most, it ups his probability of losing

So perhaps it more practical than we give it credit for

the thing is that the initial choice made isn't a random choice, it is made for a reason.

No matter what that is, it is less likely to have someone go back on their reasoning.

The question would be different and more for the statician if perhaps the contestant was giving a box at random.

even a statician is human and i would still say is likely to stick to his decision based on his initial 'reasoning' based analysis.

 

[DeaDheaD]

Yes but because one option is eliminated and an option to repick is given, the fact that if you stay with your original pick means you just repicked but with the same door, It's A,K,Q, Q is eliminated, option to repick, you stay with A, you've essentially repicked A, giving you a 50% chance between A and K.

 

[November Rain]

but that is a freeze frame analysis and isn't representative of the whole 'game'

 

[Carcharodon]

November Rain is correct!

 

[Carcharodon]

Yes but because one option is eliminated and an option to repick is given, the fact that if you stay with your original pick means you just repicked but with the same door, It's A,K,Q, Q is eliminated, option to repick, you stay with A, you've essentially repicked A, giving you a 50% chance between A and K.

You can't neglect the probability of the first pick altogether, which is what you're doing here. When you made your initial decision, you had a 1/3 chance of being correct to begin with. If you stay, it certainly is not the same as, "repicking." The door being opened doesn't mean that the initial choice never existed or occurred.

 

[Carcharodon]

Spoiler

I'm not a statistical student so perhaps this is what clouds my judgement but I thought of that, however my main problem with it is that it doesn't address the fact that you still might of chosen right in the first place... Then again I suppose the objective is to just up your probability.

Yep. It's all about probability.

 

[Majik1387]

This isnt a riddle, it's a math problem in disguise.

 

[Carcharodon]

This isnt a riddle, it's a math problem in disguise.

...as are half of the problems/puzzles posed in this thread. t:

 

[November Rain]

next puzzle please, most of us know the answers

 

[Ahura Mazda]

Here is one:

A father and son have an accident on the highway. The father expires and the son gets transported to the hospital but the attending surgeon sees him and says I can not operate on him, he is my son. How can that be?

If you have seen this before do not answer.

 

[November Rain]

too easy...

the son was adopted and his biological father is the surgeon

Spoiler

i actually know the answer, i'm just throwing alternatives your way

 

[Ahura Mazda]

I know how easy it is but i could not think of any good ones

 

[November Rain]

Here's one that's a little abstract.

ONe day before going into work, a lady decided to go and buy some new shoes. she went into a shoe store and picked up some high heels that she liked. she liked them so much that she ended up wearing them into work. Later that day, the lady died.

What was her profession and ultimately how did she die?

 

[Ahura Mazda]

A construction worker and she fell of a building