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You bet! You roll a die. If it comes up a \(6,\) you win $$\$ 100$$. If not, you get to roll again. If you get a 6 the second time, you win $$\$ 50$$. If not, you lose. a. Create a probability model for the amount you win. b. Find the expected amount you'll win. c. What would you be willing to pay to play this game?

Short Answer

Expert verified
a. The probability model for the amount you could win is: \$100 with a probability of 1/6, \$50 with a probability of 5/36, and \$0 with a probability of 25/36. \nb. The expected value or the expected amount you'll win is about $$\$23.61$$. \nc. The fair price to play this game, or the amount you'd be willing to pay to play, is the expected value, or about $$\$23.61$$.

Step by step solution

01

Create the Probability Model.

The game involves rolling a six-sided die. The chances of getting a \(6,\) which results in a winning, on any single roll are \(1/6.\) Here's how we calculate the possible outcomes and their respective probabilities:1. Winning on the first roll: The probability of rolling a \(6\) is \(1/6,\) and the payout in this case is $$\$100$$. So, the possible outcome is $$\$100$$, with a probability of \(1/6\).2. Winning on the second roll: The probability of not rolling a \(6\) on the first roll is \(5/6,\) and then rolling a \(6\) on the second roll is also \(1/6.\) Therefore, the total probability for this event is \(5/6 * 1/6 = 5/36.\) The payout for this event is $$\$50$$.3. Not winning at all: The probability of not rolling a \(6\) on the first roll is \(5/6,\) and similarly for the second roll, the total probability for this outcome is \(5/6 * 5/6 = 25/36.\) The payout for this event is $$\$0$$.
02

Calculate the Expected Value.

The expected value is the sum of all possibilities, each multiplied by its probability. \(EV = (100 * (1/6)) + (50 * (5/36)) + (0 * (25/36)) = \$16.67 + \$6.94 + \$0 = \$23.61\)
03

Determine the Fair Entry Fee.

Essentially, the fair price to play this game (i.e., the amount you would want to pay to play) is the expected value calculated in Step 2, which is $$\$23.61.$$. This would result in a net zero profit or loss over an infinite number of games, as on average, you would win exactly what you paid to play each time.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Expected Value
The concept of expected value is central to the idea of a probability model. When you're playing a game involving randomness, like rolling a die, expected value tells you what you can anticipate gaining or losing on average, if you were to play the game over and over again.

For example, in the die game mentioned, the expected value is calculated by multiplying each outcome by its respective probability and adding all these values together. With a chance to win \(100 on the first roll and \)50 on the second roll, the resulting expected value shows what you should expect to win after many rounds. It's important not to confuse expected value with the actual outcome of a single game - it's all about the long-term average.

Understanding expected value is crucial for making informed decisions in games of chance. It allows you to objectively measure the fairness of a game and to compare it with other games or investments based on their profitability or risk.
Fair Game Pricing
Fair game pricing is a term used to describe the scenario where the cost of entering a game is equal to what players can expect to win back, on average. For a game to be considered 'fair', the price to play should be set at the game's expected value.

In the die game example, the fair entry fee would be $23.61, as determined by the expected value calculation. This ensures that, theoretically, neither the player nor the host has a financial advantage over an extended period. If you charge more than the expected value, players will lose money over time, while charging less could mean a loss for the game host.

It's important for students to grasp the concept of fair game pricing as it applies to not only games of chance but to financial decisions and risk assessment in everyday life. A good understanding of this can help in making sound choices when encountering similar situations involving probabilities and outcomes.
Probability Calculations
Probability calculations are essential for determining the expected outcomes of random events. In our die game, for instance, the probability of winning the game on the first roll is calculated by dividing the number of winning outcomes by the total number of possible outcomes. Since a die has six faces, the chance of rolling a six is 1 out of 6, or approximately 16.67%.

To understand a more complex probability like not winning on the first roll but winning on the second, you need to multiply the probabilities of each independent event. The probability of not rolling a six (5 out of 6 chance) followed by the probability of rolling a six on the second roll gives us the combined chances for that scenario.

Mastering probability calculations is invaluable since they can predict how often events are likely to occur. This predictive power is leveraged in many fields, from insurance to finance, and is a fundamental skill for students looking into careers in these areas as well as in science and engineering.

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