Quote:
Originally Posted by pkdk
When an event is changed, things obviously change.
The event hasn't changed. There are 4 boxes, and 2 have a prize. There is a 50% chance of each box having a prize. You taking away 2 boxes, chosen at random, doesn't change anything. Yes, there could be no prizes, or they could both have prizes. The odds of each individual box containing a prize is still 50%.
Perhaps this will help. Here are all the possible configurations of the 4 boxes, with box 2 containing the winners.
11 22
12 12
12 21
21 12
21 21
22 11
The first pair are what remains once you've taken 2 boxes away, leaving you with these pairs to choose from:
11
12
12
21
21
22
4 times you will have a 50% chance of choosing a winner. 1 time you will have a 100% chance, and 1 time you will have a 0% chance. The average is...
...50%!