Expected Value of Rolling a Pair of Dice - Fair Price to Play

In summary, the expected value of rolling a pair of dice is 7. It is calculated by multiplying the probability of each outcome by its corresponding value and adding all of these products together. The expected value helps determine the fairness of a game and can vary depending on the rules. For a fair game with an expected value of 7, the fair price to play would be $7.
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rymatson406
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We roll a pair of dice. If the sum of the dice is 7, you pay me $28. If the sum is not 7, I pay you the number of dollars indicated by the sum of the dice. What is the price that you should pay to play the game that would make the game fair?
 
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I deleted the duplicate of this thread in the Advanced Probability subforum. We ask that you post a question only once, as doing otherwise can lead to duplication of effort on the part of our helpers. I'm sure you can understand that the time and effort of our helpers is valuable, and we don't want to see it wasted. :D

edit: I did the same with your other question.
 
  • #3
rymatson406 said:
We roll a pair of dice. If the sum of the dice is 7, you pay me $28. If the sum is not 7, I pay you the number of dollars indicated by the sum of the dice. What is the price that you should pay to play the game that would make the game fair?

Among the 36 possible results of the roll of two dice, those whose sum is k are k-1 for k ranging from 2 to 7 and 12 - (k-1) for k ranging from 8 to 12. The expected win your opponent is ...

$\displaystyle E\ \{ O \} = \frac{(1 + 2 + 3 + 4 + 5)\ 14}{36} = 5.833... \text{dollars}$

Your expected win is...

$\displaystyle E\ \{ Y \} = \frac{28}{6} = 4.666... \text{dollars}$

... and it is lower. For a fair game You should ask 35 dollars...

Kind regards

$\chi$ $\sigma$
 

FAQ: Expected Value of Rolling a Pair of Dice - Fair Price to Play

What is the expected value of rolling a pair of dice?

The expected value of rolling a pair of dice is 7. This means that if you were to roll the dice an infinite number of times, you can expect the average value to be 7.

How is the expected value calculated for rolling a pair of dice?

The expected value is calculated by multiplying the probability of each outcome by its corresponding value, and then adding all of these products together. For rolling a pair of dice, there are 36 possible outcomes and each outcome has a probability of 1/36. Therefore, the expected value is (1/36)*(2+3+4+5+6+7+8+9+10+11+12) = 7.

What is the significance of the expected value in rolling a pair of dice?

The expected value is important because it helps us understand the average outcome of a random event. In the case of rolling a pair of dice, it can help us determine if a game is fair or not. For example, if someone wants to charge you $10 to play a game where you roll a pair of dice and win $12 if you roll a 7, you can calculate the expected value to see if it is a fair price to play.

Is the expected value always the same for rolling a pair of dice?

No, the expected value can vary depending on the rules of the game. For example, if the game has a different payout for rolling a 7, the expected value will be different. However, for a fair game where the payout for rolling a 7 is equal to the cost of playing, the expected value will always be 7.

What is the fair price to play a game of rolling a pair of dice with an expected value of 7?

The fair price to play a game of rolling a pair of dice with an expected value of 7 would be $7. This means that if you were to play the game an infinite number of times, you can expect to break even. Any price lower than $7 would be considered a good deal, while any price higher would be considered a bad deal.

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