The mathematics driving tactical trading are an exact solution to a two occurrence random walk called a Martingale (which was originally developed to play roulette and blackjack). The mathematics are exact and do not include probabilities; you know what the profit outcome will be before beginning to trade. Martingales on roulette or blackjack are of marginal value because of the 46% player win percentage. However, with sideways or trending stocks the win percentage can move to 50%, 55%, or higher. If you used Martingale mathematics and played roulette or blackjack with a 55% win percentage you could easily break the bank. With stocks, that's the general idea.