Expected Value

A raffle ticket costs $1. The prize is $100, and 200 tickets are sold. The prize is dazzling — but is the ticket worth it? Not 'will I win?' (you almost certainly won't), but 'on average, over many such raffles, what does one ticket return?' That average is the expected value — the single number that tells you whether a bet, an investment, or an insurance policy is worth its price. And it's the number that quietly explains why the casino always wins.