George Szpiro

I opened the right door.

Do you want to change to the middle door?

Most people would say, well, it doesn't matter.

The chances are half-half.

There are two closed doors.

So half it's the left door, half it's the middle door.

So I don't care.

But that's actually wrong because...

At the outset, there was a one-third chance that the left door had the car and two-third chances that one of the other two doors had the car.

So when Monty Hall opened one of the other two doors, the two-thirds probability just went onto the door that was still closed.

So actually, the correct probability

see a way to look at it is there's a one-third chance that the car is behind the left door that the person chose at the outset and there's still a two-thirds chance that it's behind the closed door so it's worthwhile changing to the other door and that was a huge

outcry at the time.

Nobody believed it.

But actually, it sounds paradoxical.

There are two closed doors, so the chances should be 50-50.

But no, they are 33 and 66.

So it's worthwhile changing.

So that's a veridical paradox.

It sounds paradoxical because you'd think two closed doors, so it should be 50-50.