DislikedFor example, maybe the stock market is random. I don't know, but maybe it is. Let's assume it is for now. Then that would be an example of something random that has a positive expected change in price. How do you know that the expected change in price is positive? Well, take a look at the Dow Jones or the S&P 500 (both approximations for the stock market as a whole). They've been around for many years, and despite all the stock market crashes and bubbles bursting, the price is higher today than it was when the index started. In other words, prices...Ignored
A pure random walk cannot be traded profitable, this can also be proven formally.