Wednesday, August 06, 2008

Birthday Wager

You are at a party with a friend and 10 people are present including you and the friend. your friend makes you a wager that for every person you find that has the same birthday as you, you get $10; for every person he finds that does not have the same birthday as you, he gets $2. would you accept the wager? Why or why not?


  1. Mike, I think there is a mistake in this problem. The expected value for you is way way negative. Did you mean birth month? Even then, your expected value is little negative, but you have a greater than 50% chance of finding someone with your birth month. I could be wrong about what you were intending, but take another look.

  2. You're right, Abe. The odds here are so low the bet isn't worth it. I should have written this differently.

  3. We had this problem in probability and statistics coincidentally. Turns out if there were about 40 people at the party it would be worth the wager, for birth date itself and not just month.


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