/sci/ - Science & Math

To the 1/2 fags.

Let's assume a world with perfect probabilites.

We do this test with 90 people.

There are 3 boxes. 1/3 chance. How many get box A? 30. Box B? 30. Box C? 30.

30 people are out of the game already, they picked the box with 2 silvers.

30 people picked box A. There are 2 coins inside. 15 pick coin 1. Gold. 15 pick coin 2. Gold. All 30 stay in the game.

30 people picked box B. There is 1 gold coin inside. 15 pick coin 1. Gold. They're in the game. 15 pick coin 2. Silver. They're not in the game.

Okay so we have 45 people in the game at this stage.
30 people have box A with 2 gold coins.
15 people have box B because those are the lucky 1/2 that picked the gold coin from box B to stay in the game.

What's the probability the next pick is gold??

>Hurr its 50/50 cos you either pick the coin or you don't. 22.5 people will win.

Nope. There are 30 people in the game with box A. Only 15 who chose box B were lucky enough to stay in the game because they needed luck to not draw the silver, and they will lose on their next draw.

=> 2/3 chance of winning.

The chances of having box A and box B are not equally likely, they were equally likely to be chosen by the player initially, but then 50% of the box B pickers were culled from the game by chance. There are twice as many ways to pick box A and stay in the game than B, and box A pickers are the guys who win.

This is not a difficult concept.