Transcript: When Does 50/50 Become 50/50?

BIANCA: I’m just in time. I really don’t like it when I miss the start of a movie. There were two films that I really wanted to see. One is this new dinosaur movie and the other stars Giovanni, my favorite actor. So when I got to the box office…

BIANCA: I don’t know which one to pick? I’ll flip a coin: heads “dinosaurs,” tails “Giovanni.” (Flips coin) “Heads.” I wonder what will happen if I try that again? (Flips coin) “Heads.” Again. (Flips coin) “Heads”. It doesn’t seem fair. Poor Giovanni didn’t come up once! Is it fair? Even steven? Fifty fifty? (Flips coin) Finally! But that’s three heads to one tail. It doesn’t seem fair. So I decided I wanted to do some research on why Giovanni didn’t win half the time.

BIANCA: “Fred’s Encyclopedia of Probability!” Let’s see. One in a million, one in a thousand, one in a hundred… Here we go, fifty fifty. When flipping a fair coin about half the time it will be heads and about half the time tails. See note, see note… Note. This will only happen if you flip the coin many times. Well I flipped the coin four times but I got three heads to one tail, and that’s not half and half. (reads book) You have to flip a lot more than four times.

BIANCA: Hey do you remember I asked you to hold my place?

GIRL IN LINE: Yes.

BIANCA: Okay, great. Thanks. Wait a minute! Flipping ten coins one time is the same as flipping one coin ten times. Excuse me, I’m trying to find out if I flip a coin a lot of times, will the results really be fifty fifty? Heads about half the time and tails about half. Will you help me? C’mon, it will only take a minute.

BIANCA: How many heads raise your hands? Hmm… only three heads and seven tails. With ten coin flips, that’s still not very close to fifty fifty. I need to try this with a lot more people.

BIANCA: This better work. Can I borrow that for a second?

MAN: Sure.

BIANCA: Thank you. Hello, I need everyone to flip a coin to see if heads really does come up about half the time. Just the people who got heads, raise your hands.

BIANCA: How many people here?

MAN: Three hundred and fifty paid at the gate.

BIANCA: Wow! Then it is true. I think I could say that’s pretty much fifty fifty. Thanks. Fred’s encyclopedia was right. If you flip a coin just a few times it might not be close to fifty fifty. But if you flip lots of times, like three hundred and fifty, then it will be closer to heads about half the time and tails about half.