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Physics Quiz
Win a Car

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The show master presents 3 doors to the candidate:

"Behind one of these doors there is a car you can win. Behind the others there are goats.
What is your choice ?"


The candidate makes his choice, e.g. number 1.

Show master:
"I know the door with the car behind, but I'll open a door with a goat."

e.g. number  3.

Show master:
"Do you still go for the same door or do you want to revise your choice ?"


How would YOU decide ?

   No, I won't change my mind, my chance would still be 1/3.

    No, I won't change my mind, my chance will diminish.

    Regardless of whether I switch, my chance will rise to 1/2.

    Yes, I want to change doors, because my chance will rise to 2/3.

    Yes, I want to change doors, because my chance will rise, but to another value than 1/2 or 2/3.


 Enable "JavaScript" to get the solution !


Result (until 6/17/98): 47 of 107 submissions were correct.


Die Anregung zu dieser Aufgabe verdanke ich:
Gero von Randow: "Das Ziegenproblem", Denken in Wahrscheinlichkeiten
science sachbuch, rororo 9337

 If you can't make up your mind - play the game !


  1. Choose one of the doors with your first mouse click. Your choice will be marked green;
    the show master opens one of the the two doors remaining (marked by a red frame).
  2. Confirm your choice with a second mouse click or, if you changed your mind, select the black door.
    Now the result will be shown and displayed as text.
  3. Click on "new game"

The button "clear" will reset all previous results !

Repeat and compare the results with and without changing your choice !

Hint: the Java console shows the distribution of the random numbers (1,2,3).


   [List of quiz problems]

Detailed discussions of the problem:
Monty Hall Dilemma
The Monty Hall Problem
Three Door Puzzle




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Last modified : 2010, May 13