Monty Hall Problem

Monty Hall Problem

What is it?

The Monty Hall problem is a probability puzzle in which a contestant must choose one of three doors, behind one of which is a prize, and is then given the option to switch their choice after one of the remaining doors is revealed to be empty. The counter-intuitive solution is that switching the choice increases the contestant's chance of winning.

The Monty Hall Problem is a probability puzzle named after the host of the television game show "Let's Make a Deal," Monty Hall. The problem demonstrates a counterintuitive aspect of probability that can be difficult to grasp at first. Here's a simple example to explain the concept:

Imagine you're a contestant on a game show. The host, Monty Hall, presents you with three doors: Door A, Door B, and Door C. Behind one of the doors is a brand new car, and behind the other two doors are goats. Your goal is to choose the door with the car behind it.

Here's how the game plays out:

  1. You choose one of the doors, say Door A.
  2. Monty, who knows what's behind each door, opens one of the other two doors to reveal a goat (for example, Door B).
  3. Monty then gives you the option to either stick with your original choice (Door A) or switch to the remaining unopened door (Door C).

The Monty Hall Problem asks: Should you stick with your original choice, switch to the other door, or does it not matter?

Intuitively, it might seem like there's a 50-50 chance of winning the car, no matter if you stick or switch. However, the surprising result is that you actually double your chances of winning the car by switching doors.

Here's why:

When you first choose a door, you have a 1 in 3 chance of picking the car, and a 2 in 3 chance of picking a goat. If you stick with your original choice, your probability of winning the car remains 1 in 3. If you switch, you win the car if your original choice was a goat, which had a 2 in 3 chance of happening. So by switching, your probability of winning the car is actually 2 in 3. In summary, the Monty Hall Problem demonstrates that in this specific game show scenario, you're better off switching doors after Monty reveals a goat behind one of the unchosen doors. This counterintuitive result highlights how our intuition about probability can sometimes be misleading.

The Monty Hall Problem is a classic probability puzzle based on the television game show "Let's Make a Deal" hosted by Monty Hall (Selvin, 1975). The problem illustrates the importance of conditional probability and showcases how human intuition can often be misleading when it comes to probabilistic reasoning (Tversky & Kahneman, 1974).

In the problem, a contestant is asked to choose one of three doors. Behind one door, there's a car, and behind the other two doors, there are goats. After the contestant picks a door, the host (who knows the contents behind each door) opens one of the remaining doors to reveal a goat. The contestant is then given the option to either stick with their original choice or switch to the other unopened door.

The Monty Hall Problem asks whether it is more advantageous for the contestant to stick with their initial choice, switch doors, or if the decision doesn't matter. The counterintuitive result is that the contestant doubles their chances of winning the car by switching doors, as the probability of winning increases from 1/3 to 2/3.

This problem can be related to several principles and scientific topics:

  1. Conditional probability and Bayes' theorem: The Monty Hall Problem can be analyzed using conditional probability and Bayes' theorem (Bayes & Price, 1763), which allows us to update our probabilities based on new information. In the context of the problem, after Monty reveals a goat, we can update our probabilities for the car being behind each door using Bayes' theorem, which shows that switching doors increases the likelihood of winning.

  2. Behavioral economics and decision-making: The Monty Hall Problem is often cited in the context of human decision-making and behavioral economics (Tversky & Kahneman, 1974). People tend to rely on heuristics, or mental shortcuts, when making decisions, which can lead to incorrect judgments in situations involving probability. The Monty Hall Problem exemplifies how our intuition might suggest that sticking or switching doesn't matter (as both options seem to have a 50% chance), while the actual probabilities tell a different story.

  3. Randomized algorithms and exploration-exploitation trade-off: The Monty Hall Problem can be seen as a simple instance of a more general class of problems involving randomized algorithms and the exploration-exploitation trade-off in artificial intelligence and reinforcement learning (Sutton & Barto, 2018). In these problems, an agent must balance the need to explore new possibilities (in this case, switching doors) with the need to exploit existing knowledge (sticking with the initial choice). The Monty Hall Problem highlights the importance of updating beliefs and taking calculated risks based on new information to maximize rewards.

In summary, the Monty Hall Problem is a fascinating probability puzzle that highlights the importance of conditional probability, challenges our intuition, and is connected to various principles and scientific topics, including decision-making, behavioral economics, and artificial intelligence.

References

  • Bayes, T., & Price, R. (1763). An essay towards solving a problem in the doctrine of chances. Philosophical Transactions of the Royal Society of London, 53, 370-418.
  • Selvin, S. (1975). A problem in probability (letter to the editor). The American Statistician, 29(1), 67.
  • Sutton, R. S., & Barto, A. G. (2018). Reinforcement learning: An introduction. MIT Press.
  • Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185(4157), 1124-1131.