If you’ve seen at least one card trick in your life, you’ve probably seen this one. You pick out a card, put it back magicians rummages through the deck, pulls out a card, exclaims, “Is this your card?” That one.
When I was younger, I studied math at the University of Toronto and so I loved this explanation by UK math teacher, author and comedian, Matt Parker about the math behind about guessing what card someone chose. Because as it turns out that with just about everything to do with probability and statistics, that our intuitions are almost always wrong. And not just a little bit wrong, but wrong by a lot.
Now of course no sensible magician would do this trick by guessing. There has to be something else going on. But they might pretend they were guessing for dramatic effect. You never can trust those magicians.