Q&A for How to Calculate an Expected Value

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  • Question
    You play a gambling game with a friend in which you roll a die. If a 1 or 2 comes up, you win $7. Otherwise you lose $3. What is your expected value for this game?
    Community Answer
    The expected value is the average of the six equally likely outcomes, (+7+7-3-3-3-3)/6 - it simplifies to $1/3.
  • Question
    Two dice are thrown simultaneously. What is the probability of getting a sum less than 3?
    Community Answer
    1 in 36. Each die would have to show "1" in order to get a sum less than 3. That means that only one outcome would be a desired outcome. There are 36 possible outcomes (6 x 6). So the probability of a successful outcome is 1 in 36.
  • Question
    A standard cubical die is thrown twice. How do I calculate the probability that two even numbers are thrown?
    Donagan
    Top Answerer
    The probability that the first throw will come up even is 3 in 6. The probability that the second throw will come up even is also 3 in 6. 3/6 multiplied by 3/6 is 9/36, which reduces to 1/4. The probability of throwing two even numbers is 1 in 4.
  • Question
    How do I calculate the mean of a group of numbers?
    Donagan
    Top Answerer
    The mean is the average. Add the numbers together, and divide the sum by the number of numbers.
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