Swapping problems

[huy.duong@ctsu.ox.ac.uk]

Dear friends,

The 2-envelope and 3-box-1-prize problems
each involves only one probabilistic process (the
initial choice) and an optional process which is
deterministic (swapping always turns the good choice
into the bad one and vice versa). 

The prob of each (good/bad) state after the initial choice is easy. 

The swapping changing each of these states to any other state 
with prob 1 or 0.
 
For the 2-envelope problem, people go up the wrong track when
they they don't realise that the swapping process is deterministic
and they assign a probability which is really the initial/final 
probablility to this process. The result is the incorrect 
recommendation of swapping.

Huy