Pick a card: Mike and Dave play the following game. Mike picks a card from a deck of cards. If he selects a heart, Dave gives him $5. If not, he gives Dave $2.
Mike's net winnings are
+$5 if he selects a heart or -$2 if he doesn't select a heart
Mike's expectation =
(net winnings if he gets a heart)*(probability of getting a heart)
plus
(net winnings if he doesn't get a heart)*(prob of not getting a heart)
Probability of Mike getting a heart = or
Probability of Mike NOT getting a heart = or
So,
Mike's expectation =
If they continue to play the game many times, in the end
Mike will have averaged LOSING 25 cents per game.
----------------------------
Dave's net winnings are
-$5 if Mike selects a heart or +$2 if he doesn't select a heart
Dave's expectation =
(net winnings if Mike gets a heart)*(probability of Mike getting a heart)
plus
(net winnings if Mike doesn't get a heart)*(prob of Mike not getting a heart)
Probability of Mike getting a heart = or
Probability of Mike NOT getting a heart = or
So,
Dave's expectation =
If they continue to play the game many times, in the end
Dave will have averaged WINNING 25 cents per game.
Edwin