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Playing the Numbers. The numbers racket is a wellentrenched illegal gambling operation in most large cities. One version works as follows: you choose one of the 1000 three-digit numbers 000 to 999 and pay your local numbers runner a dollar to enter your bet. Each day, one three-digit number is chosen at random and pays off \(\$ 600\). The mean payoff for the population of thousands of bets is \(\mu=60\) cents. Joe makes one bet every day for many years. Explain what the law of large numbers says about Joe's results as he keeps on betting.

Short Answer

Expert verified
As Joe bets every day, over many years his average payoff per bet will approach the expected payoff of 60 cents, consistent with the Law of Large Numbers.

Step by step solution

01

Understand the Exercise Scenario

Joe participates in an illegal gambling operation where he bets on a three-digit number daily. Each number from 000 to 999 has an equal chance of being selected, and the payoff for a winning bet is \(\\(600\). Joe pays \(\\)1\) for each bet, resulting in a net loss of \(\$0.40\) (since the mean payoff is \(\mu=60\) cents).
02

Define the Law of Large Numbers (LLN)

The Law of Large Numbers states that as the number of trials increases, the sample mean of the results will converge to the expected value (or population mean). This concept suggests that over a long period, Joe's average outcome per bet will approach the expected amount of loss per bet.
03

Calculate Expected Value and Application of LLN

Joe's expected value for each bet is \(60\) cents, meaning on average, Joe loses \(\\(0.40\) (because he pays \(\\)1\) and wins \(\\(0.60\) on average). According to the LLN, as Joe continues betting every day over many years, the average payoff of his bets will converge to 60 cents per bet, indicating consistent losses on his \(\\)1\) bets.

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Key Concepts

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

Probability
Probability is a fundamental concept in understanding scenarios like gambling, where chance plays a significant role. In the numbers game Joe is involved in, each three-digit number from 000 to 999 has an equal chance of being chosen. This gives us a probability of 0.001, or 1 out of 1000, that any specific number Joe picks will win.

Probability helps quantify the likelihood of an event occurring. Here, it indicates how often Joe might expect to win by sheer chance. However, with such a low probability of winning, it's clear why people generally lose money in this type of gamble. Without relying on probability, these games would seem much more unpredictable and deceitful. Armed with the knowledge of probability, we can approach such bets with a clear understanding of the risks, and more importantly, the rare likelihood of a favorable outcome.
Expected Value
The expected value is a crucial concept for assessing the fairness of a game or gamble. It represents the average amount one would expect to win or lose per bet if the same bet could be repeated many times. In Joe's situation, the expected value per bet is 60 cents.

This means that for each dollar Joe bets, he can expect to get back 60 cents on average, indicating an average loss of 40 cents per bet. Calculating the expected value helps Joe understand that over time, he isn’t making a profit, but rather losing 40 cents with each risk. Expected value is not just a theoretical concept; it practically reveals how choices made under uncertainty can translate into long-term outcomes.
  • Total payout for a win: $600
  • Probability of winning: 0.001
  • Expected gain per bet: $0.60 (or 60 cents)
Understanding this concept helps individuals like Joe recognize the adverse long-term impact of continual betting.
Gambling Odds
Gambling odds provide insights into the ratio between the amount bet and the potential profit. In Joe's numbers game, one can decipher the unfavorable odds that come with the bet. When gambling, odds reflect how much risk is involved compared to the reward.

In every bet Joe makes, he risks $1 for a chance of winning $600. However, given that the actual chance (probability) of the three-digit number being selected is 1 in 1000, the odds do not work in Joe's favor. This imbalance between risking a dollar and the rather bleak probability of winning highlights that the house, in this case, heavily stacks the odds against the player.

Understanding the odds can prevent illusions about potential winnings and reveals why gambling, especially when odds are skewed, generally leads to loss. For Joe, knowing the odds means grasping how frequently he would win compared to the money he'd routinely lose. Therefore, gambling odds serve as a reality check, demonstrating that the rare wins cannot outweigh the consistent losses over numerous bets.

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Most popular questions from this chapter

Roulette. A roulette wheel has 38 slots, of which 18 are black, 18 are red, and two are green. When the wheel is spun, the ball is equally likely to come to rest in any of the slots. One of the simplest wagers is to choose red or black. A bet of \(\$ 1\) on red returns \(\$ 2\) if the ball lands in a red slot. Otherwise, the player loses the dollar. When gamblers bet on red or black, the two green slots result in losses. Because the probability of winning \(\$ 2\) is \(18 / 38\), the mean payoff from a \(\$ 1\) bet is twice \(18 / 38\), or \(94.7\) cents. Explain what the law of large numbers tells us about what will happen if a gambler makes very many bets on red.

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The Medical College Admission Test. Almost all medical schools in the United States require students to take the Medical College Admission Test (MCAT). To estimate the mean score \(\mu\) of those who took the MCAT on your campus, you will obtain the scores of an SRS of students. The scores follow a Normal distribution, and from published information, you know that the standard deviation of scores for all MCAT takers is 10.6. Suppose that (unknown to you) the mean score of those taking the MCAT on your campus is \(500.0\). a. If you choose one student at random, what is the probability that the student's score is between 495 and 505 ? b. You sample 25 students. What is the sampling distribution of their average score \(x\) ? c. What is the probability that the mean score of your sample is between 495 and 505 ?

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The Bureau of Labor Statistics announces that last month it interviewed all members of the labor force in a sample of 60,000 households; \(3.5 \%\) of the people interviewed were unemployed. The boldface number is a a. sampling distribution. b. statistic. c. parameter.

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