A friend offers you an opportunity to buy a raffle ticket for $50. There were 1,000 tickets sold and the lucky winner will receive $20,000. Your friend promises you that if you don’t win, he’ll give you a $20 refund.

A friend offers you an opportunity to buy a raffle ticket for $50.

There were 1,000 tickets sold and the lucky winner will receive $20,000.

Your friend promises you that if you don’t win, he’ll give you a $20 refund.

Should you buy a ticket?

Ignore altruism, as well as incentives to cooperate – such as reciprocity and reputation. Just focus on the numbers.