You are presented with two identical envelopes, each containing money. One envelope has twice as much money as the other. You are allowed to choose one envelope and keep the money it contains.
After you choose an envelope, you are given the option to switch to the other envelope. Should you switch? Is there a strategy that gives you the highest chance of getting the envelope with the most money?
This is a classic problem in probability theory known as the two envelopes problem. The answer to whether you should switch or not depends on the strategy you adopt. However, there is no clear consensus on the optimal strategy for this problem, as different strategies can lead to different outcomes.
One approach to solve this problem is to consider the expected value of each envelope. Let’s assume that the first envelope you choose contains X amount of money, and the second envelope contains either 2X or X/2 with equal probability. Then, the expected value of the first envelope is:
E(X) = (X + 2X)/2 = 3X/2
The expected value of the second envelope is:
E(2X or X/2) = (1/2) * (2X) + (1/2) * (X/2) = 5X/4
Since the expected value of the second envelope is higher than the expected value of the first envelope, it might seem that you should always switch to the other envelope to maximize your chances of getting more money.
However, some argue that the problem is ill-defined, as there is no clear way to assign a probability distribution to the money in the envelopes. For instance, if the amount of money in the envelopes follows a uniform distribution, the expected value calculation above would not apply.
Another strategy is to use a “mixed” strategy, where you switch to the other envelope with a certain probability, say p, and keep the envelope you initially picked with probability 1-p. By varying the value of p, you can try to optimize your expected payoff.
Ultimately, the choice of strategy depends on your personal preferences and beliefs about the probability distribution of the money in the envelopes.