a The expected value is the probability of a side multiplied by the earnings received by getting that side.
B
b Multiply the expected earnings from one coin flip by the number of times she flips the coin.
A
a - $ 1.50
B
b - $ 12
Practice makes perfect
a A coin has two sides, which means the probability of flipping either side is 12.
P(heads)=1/2 [0.8em]
P(tails)=1/2If we multiply the probability of flipping each side by their respective value and add the products, we get the expected value from one coin flip.
Event
P
Value
P* Value
Expected Value
Heads
1/2
4
1/2* 4
2
Tails
1/2
-7
1/2* ( -7)
-3.5
The expected earnings from one flip of the coin is the sum of the expected value for each side.
b From Part A we know that the expected value from one coin toss is - $1.50. Therefore, after 8 coin tosses the expected value should be this number multiplied by 8.
