# Exploring the monty hall problem

### June 5 2024

Author: Wilson Chen

Edited by Kevin Guo

The Monty Hall problem is a famous probability puzzle based on a game show scenario.

**Exploring the Monty Hall Problem**

The Monty Hall problem is a famous probability puzzle based on a game show scenario. It's named after Monty Hall, the original host of the American television game show "Let's Make a Deal." This problem is both fun and counterintuitive, making it a great example of how our instincts about probability can sometimes lead us astray.

**The Problem Explained**

Here's how the Monty Hall problem works:

1. You are a contestant on a game show. There are three doors: behind one door is a car (the prize), and behind the other two doors are goats.

You pick one of the three doors, hoping to find the car.

2. The host, Monty Hall, who knows what’s behind all the doors, opens one of the other two doors, revealing a goat.

3. Monty then gives you a choice: stick with your original door or switch to the other remaining closed door.

The question is: should you stick with your original choice, or should you switch? Which strategy gives you the best chance of winning the car?

**The Solution**

Intuitively, many people think that it doesn't matter whether you switch or stay, assuming the chances are equal (50/50). However, probability theory tells us a different story.

- When you first choose a door, you have a 1/3 chance of picking the car and a 2/3 chance of picking a goat.
- After Monty reveals a goat behind one of the other two doors, the probabilities change, but not in the way you might expect. The key is that Monty's action of revealing a goat provides additional information. If you initially picked the car (1/3 chance), switching will make you lose. If you initially picked a goat (2/3 chance), switching will make you win the car.

So, by switching, you have a 2/3 chance of winning the car, compared to a 1/3 chance if you stick with your original choice. Thus, you should always switch!

**Examples**

Let's walk through an example to make this clearer.

- Starting with Door 1: You pick Door 1. The car is behind Door 3. Monty reveals a goat behind Door 2. If you switch to Door 3, you win the car.
- Starting with Door 2: You pick Door 2. The car is behind Door 1. Monty reveals a goat behind Door 3. If you switch to Door 1, you win the car.
- Starting with Door 3: You pick Door 3. The car is behind Door 2. Monty reveals a goat behind Door 1. If you switch to Door 2, you win the car.

In each case, switching doors after Monty reveals a goat behind one of the unchosen doors gives you a better chance of winning.

**Why is it So Counterintuitive? **

The Monty Hall problem is counterintuitive because our brains are not naturally good at handling conditional probabilities. We tend to think that the odds are equal once a door is eliminated, but we fail to account for the fact that Monty's action of revealing a goat provides crucial information that affects the probabilities.

**Conclusion**

The Monty Hall problem is a fantastic illustration of the sometimes surprising nature of probability. It shows that our intuitive judgments can often be wrong, and it highlights the importance of understanding the underlying mathematics to make the best decisions. Next time you're faced with a similar choice, remember the Monty Hall problem and consider switching – it just might lead you to victory!

**Sources**:

Monty Hall Problem | Brilliant Math & Science Wiki. https://brilliant.org/wiki/monty-hall-problem/. Accessed 5 June 2024.

Understanding the Monty Hall Problem – BetterExplained. https://betterexplained.com/articles/understanding-the-monty-hall-problem/. Accessed 5 June 2024.