Healthcare Economics: Five of ten people earn 0$,

Question

 four earn $100 and one loses $100. What is the expected payoff? What is the variance of the payoff?

Answer 1

Expected is just the mean so (400-100)/10=30

Var is a bit more complicated but basically its Sum each variable squared / number of variables - mean squared

so that's (10,000 x 4 + 10,000) / 10 = 5,000 then subtract 30 squared or 900 

Mean=30

Var = 4100