a5areal

我唔認同.......我覺得點都係1/2 機會.....

Providence2

其實，都係三分之一幾會姐......

hkcchk

the answer should be 1/2.  It is because no matter what, the empty will be opened after your choice.  That means one of the empty door has been excluded.  The question is that the probablity of your first choice and second choice is the same that is 1/2 and they are independ.  The probability will not increase as you will not be able to choose the one to be opened with car !

I want to change me answer.  It should be 1/3.  It is because of in the first choice, the probability of selecting the door with car is 1/3.  After opened a empty door, the probability seems shifted to the rest of the two door to become 1/2 but the probability of your original choice is still 1/3.  So change of selection is a good decision.

To illustrate the answer more clearly. Say there are 10 doors.  You have made your selection and the probability to choose the one with car is 1/10.  The host opened the rest of 8 empty door.  If the selection remain unchange, the probability is still 1/10 as it does not change even some empty doors are opened.  So, change of selection is correct.  I support the brillant with IQ228.

[ Last edited by hkcchk on 2007-3-20 at 11:19 PM ]

PG-13

Originally posted by kaichun88 at 2007-3-16 05:26 PM:


The problem has mentioned that ...

Right, but i am saying "AFTER" the host opening the door but "WITHOUT" knowingly which door is the winning door

艾力克

Originally posted by sakura310 at 2007-3-14 07:42 PM:
playplay,正因為這樣,我才不要將正確...話唔定佢會話唔識計
例如3x=6,求2x=?
佢可能會將2=x代入去2x,得到xx,佢會話解唔到答案都唔定 XD

2x點都係4, 唔會錯

harvey22

I give up the more i read the more confuse i get.....

i am juz a dumb one

279x

Originally posted by lilirayhk at 2007-3-14 01:15 PM:
答案一定係1/3。我想問題重點係在於 ...

唔係呀，你講得好清楚呢。如果玩遊戲0既人一開始就決定會揀主持開剩的門，咁只要佢一開始揀中空的門就會中奬，而空的門有2所以機會係2/3，如果佢堅持要自己開始時所揀的門，咁機會只有1/3。

[ Last edited by 279x on 2007-3-21 at 01:49 AM ]

279x

Originally posted by netharmon at 2007-3-20 01:15 AM:
n = 開始時幾多度門選擇, 由始至終不...

要係無論有幾多度門，主持都係開淨兩度門，你的答案先至正確。

yorker

改唔改變選擇, 都改唔到機率啦~
已經由一開始1/3, 開左1道門之後, 就變左1/2~

所以中獎機會提高,
並唔係因為改變選擇,
係因為開左道門~ ﹙肯定左1道門無）

sweetcat

越講越複雜
我越睇越唔明

個選門遊戲係1/3中
如果唔換，即係第2次的take走一個唔中的門變得無意義
因為如果唔換(保持第1選擇)，中既機會會同未take走之前一樣，都係1/3

但如果玩者存心會換
o甘第1次選門的時候，就不是要選一個會中的門了，而是去選一個不會中的門(2/3機會)
因為選了個不中的，在第2 round主持take走一個唔中的門後
就可以去換剩下的中的那一個
所以我覺得換，就有2/3機會中架車

如此類推，如果有100個門，第1 round選個不中的就是99/100了
絕對比選中的1/100容易。

我是從玩者(選門的人)的角度去看
如果唔係一早決定第2 round換唔換
等到第2 round先再諗換唔換，感覺上真係好似變左1/2