The Motley Fool Discussion Boards

Previous Page

Investment Analysis Clubs / Macro Economic Trends and Risks

URL:  https://boards.fool.com/this-explanation-made-the-most-sense-to-me-30398170.aspx

Subject:  Re: 5 Statistics Problems To Change Your View Date:  11/25/2012  12:10 PM
Author:  jwiest Number:  409521 of 567998

This explanation made the most sense to me:

http://en.wikipedia.org/wiki/Monty_Hall_problem

That switching has a probability of 2/3 of winning the car runs counter to many people's intuition. If there are two doors left, then why isn't each door 1/2? It may be easier to appreciate the solution by considering the same problem with 1,000,000 doors instead of just three (vos Savant 1990). In this case there are 999,999 doors with goats behind them and one door with a prize. The player picks a door. His initial probability of winning is 1 out of 1,000,000. The game host goes down the line of doors, opening each one to show 999,998 goats in total, skipping over only the player's door and one other door. The host then offers the player the chance to switch to the only other unopened door...
...
Intuitively speaking, the player should ask how likely is it, that given a million doors, he or she managed to pick the right one. It's as if Monty gives you the chance to keep your one door, or open all 999,999 of the other doors, of which he kindly opens 999,998 for you, leaving, deliberately, the one with the prize. Clearly, one would choose to open the other 999,999 doors rather than keep the one.


Also, this amusing note:

Interestingly, pigeons make mistakes and learn from mistakes, and experiments show that they rapidly learn to always switch, unlike humans (Herbranson and Schroeder, 2010).

Of course, Herbranson and Schroeder should note that humans are not regularly stuck in a cage and asked to peck for food, or I imagine we'd come to the same conclusion rather quickly. Practical experience modifies "common sense".
Copyright 1996-2019 trademark and the "Fool" logo is a trademark of The Motley Fool, Inc. Contact Us