Quote from illiquid:
50/50 (greater than, less than) is an illusion in the markets -- either you are right or you are wrong for any given trade. You can try to reduce any given opportunity into a game of probabilities, but most resort to that because they have nothing better. Sure, in retrospect you can say a good trader will have a greater "expectation" than a poor trader, but that has nothing to do with the probabilities of the next trade. I'm sure many will disagree. Take the reaction of crude oil after thursday's report -- where is the 50/50 in that? Buying the instant right after the report, or selling into the spike the followed: what entries, what targets, what pain thresholds constitute "greater than 50/50"?
The point is, learning about what does work and what doesn't in the markets really never boils down to probabilities at all, but instead revolves around sound concepts and flat-out experience. It's those who focus on the rear-view derivative (aka TA), as opposed to the impetus behind market movement, who deal in terms of probabilities in general, because they find nothing else to analyze except the results of their own trades.