Article courtesy of Forex BulletProof
It will be no surprise to hear that the best foreign exchange trading systems are the ones which make cash! The issue is simply how to identify which those are, and in particular, the simplest way to decide which system will be the best for an individual trader, i.e.
First let’s cross out some systems that never make money for anyone, at least not in the long term. These are the sort of systems that gamblers sometimes call loss recovery systems. They involve varying the chance according to whether the last trade won or lost. The idea is that if your last trade lost, then your next is likelier to win, so you take a bigger position. Statistics disprove it every time. Gamblers lose their shirts on these systems and it would be crazy for a currency exchange trader to employ a system like that. So with that rant out of the way, let’s take a look at how to identify a profitable system. To do that we will introduce the concept of edge.
Edge is the measure of a system’s returns over a time period. It is a simple calculation but you do need a fair number of results to gauge it from. Back testing is a good technique to get those results. Edge is just the likelihood of a win multiplied by the average profit on a winning trade, minus the probability of a loss multiplied by the average loss on a bad trade. Results are calculated after taking away the spread and any other per trade costs.