Monty Hall Paradox

About Let's Make a Deal and the Monty Hall Paradox

History of Let's Make a Deal:

"Let's Make a Deal" is an American television game show that originated in the 1960s. It was created and produced by Stefan Hatos and Monty Hall, who also served as the show's host. The show first aired on December 30, 1963, on NBC, and later on ABC, CBS, and in syndication. The basic format involves contestants making deals with the host to trade items or choose between hidden prizes behind doors, boxes, or curtains, often with the possibility of winning big prizes or receiving undesirable "zonk" prizes.

The Monty Hall Problem:

The Monty Hall problem, also known as the Monty Hall paradox, is a probability puzzle based on a scenario that appeared on the show. The classic version of the problem is as follows:

  1. A contestant is presented with three doors. Behind one door is a car (the prize), and behind the other two doors are goats.
  2. The contestant chooses one door, say Door A.
  3. Monty Hall, who knows what's behind each door, opens another door, say Door B, which has a goat.
  4. The contestant is then given the option to stick with their original choice (Door A) or switch to the remaining unopened door (Door C).

The puzzle asks: Is it to the contestant's advantage to switch their choice?

Solution to the Paradox:

Mathematically, it is to the contestant's advantage to switch doors. When the contestant first picks a door, there is a 1/3 chance they picked the car and a 2/3 chance they picked a goat. When Monty reveals a goat behind one of the other two doors, the probability of winning by switching is 2/3, whereas the probability of winning by staying with the initial choice is 1/3. This counterintuitive result is often surprising to many people.

Marilyn vos Savant and the Controversy:

The Monty Hall problem gained widespread attention in 1990 when Marilyn vos Savant, who holds the record for the highest IQ, addressed the problem in her "Ask Marilyn" column in Parade magazine. She presented the problem and explained that switching doors increases the contestant's chances of winning.

Response from Mathematicians:

Vos Savant's explanation received thousands of letters, many of them from readers who disagreed with her solution. Among the respondents were numerous mathematicians and professors who argued that her solution was incorrect. This widespread disagreement highlighted how counterintuitive the solution is, even for those well-versed in probability and mathematics. Over time, however, many mathematicians and statisticians verified her explanation and used the problem to illustrate important concepts in probability theory and decision-making.

Impact and Legacy:

The Monty Hall problem remains a popular example in teaching probability and statistics. It illustrates the importance of considering all available information and understanding conditional probabilities. The controversy surrounding vos Savant's column also demonstrates how even experts can struggle with counterintuitive problems, underscoring the value of rigorous mathematical reasoning.

Play the Game

To play this game, first specify how many doors you'd like to use. The classic version of the game uses 3 doors but the intiution behind the probability calculation is easier to see as you increase the number of doors. Try it with 100 doors and see if the logic starts to make sense.

Now that the number of doors is specified, play proceeds as follows:
  1. The contestant selects one of the doors by clicking on it.
  2. The host opens one of the non winning doors to reveal a goat.
  3. The contestant can decide to stay with their original selection (which will be green now) or to switch to the other unopened door (which will still be brown).
  4. The user clicks the "Reveal" button to open the doors and see if the prize (a treasure chest) is behind the door they selected.
  5. Click the "Submit" button to reset the game.
Simulate the Game

Simulating the game allows you to play it a large number of times very quickly. This helps demonstrate the probability of winning when staying and when switching. The number of doors and number of times the game is simulated is specified by the user.

First choose the number of doors (classic version is 3) and then specify the number of times the game is to be played. The winning percentage computed as (number of wins)/(number of simulations) is tabulated and charted for each play. As the number of simulations increases, the total win percentages should converge to 1/(number of doors) when the contestant stays with their original pick and to 1 - (1/(number of doors)) when the contestant switches from their original pick.