Another probability “paradox”, the two-envelope problem1, goes like this: Before you are two envelopes, A and B. One of them contains $X and the other $2X (which is equivalent to $Y/2 and $Y). You pick one envelope and are (1) asked if you would like to keep it or switch, or (2) open it, view its contents, and then asked if you would like to keep it or switch. Which strategy, keeping or switching, is likeliest to win you the big bucks? No peeking solution The traditional paradoxical solution to (1) is to argue this. Suppose you pick A, which...