## [REBOL] Re: My Statistical Thoughts on Monty Hall Problem (non-REBOL)

### From: bga:bug-br at: 19-Dec-2001 16:48

From: "alan parman" <**[reboler--programmer--net]**>

> Seems to me that switch/win probability = 2/3 is the same as saying that a

fair coin will come up with heads or tails

>more often depending on which one is the winner.
>
> Please help me understand the difference between the two scenarios.

Instead of thinking about 3 doors, thing about 10000 doors:
1 - You pick one door.
2 - The other guy picks 9998 (none of them has the prize) and leaves only
one door.
Would you switch or not?
When you did your first pick, you have 1/10000 chances of winning and the
change that the prize would be in one of the other 9999 doors is 9999/10000.
In other words, the prize *WILL BE* in a door that is not the one you choose
(a 9999/10000 chance is enough to me to say that).
Now, the other guy excluded 9998 doors and the second group only has one
door now... But as we saw above, the probabitily that the prize is in this
second group is 9999/10000. So the probability that the prize is in this
single door is 9999/10000 and in the door you choose is 1/10000. That's why
you *MUST* change to the other door. :)
-Bruno