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Question
in a game you flip a coin twice, and record the number of heads that occur. you get $15 for 2 heads, pay $3 for 1 head, and pay $2 for no heads. what is the expected value for the amount youll win/lose per turn? write the answer without the $
Step1: Calculate the probability of each outcome
When flipping a coin twice, the sample space is \(S=\{HH, HT, TH, TT\}\), so \(n(S) = 4\).
- Probability of \(2\) heads (\(P(2H)\)): There is \(1\) outcome (\(HH\)) with \(2\) heads. So \(P(2H)=\frac{1}{4}\).
- Probability of \(1\) head (\(P(1H)\)): There are \(2\) outcomes (\(HT,TH\)) with \(1\) head. So \(P(1H)=\frac{2}{4}=\frac{1}{2}\).
- Probability of \(0\) heads (\(P(0H)\)): There is \(1\) outcome (\(TT\)) with \(0\) heads. So \(P(0H)=\frac{1}{4}\).
Step2: Use the expected - value formula \(E(X)=\sum_{i}x_{i}P(x_{i})\)
Let \(x_{1} = 15\) (for \(2\) heads), \(x_{2}=- 3\) (for \(1\) head, since it's a loss), \(x_{3}=-2\) (for \(0\) heads, since it's a loss).
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